You have four answers, not two. Here is what each one actually does to the other person's record.
Confirm puts the fact you confirmed on the record. Automatic checks then decide whether it counts as independent evidence.
Confirm with a correction does the same, with the detail you corrected. It counts exactly as an uncorrected confirmation would.
Decline puts nothing on the record. No mark, no event, no complaint. The work simply stays unconfirmed.
Ignore puts nothing on the record either. It sits waiting, and silence is never turned into a yes.
Confirming
You are saying one thing happened. That is all you are saying.
Your answer is recorded against that record. Whether it also counts as independent evidence is decided by checks on Credda's side. A confirmation can be recorded and still not count, and neither of you is told which check applied.
Nothing you enter becomes a rating. There is an optional question about what you were to the person, such as client, customer, manager or colleague. It is optional, it is never scored, and it is never shown beside a single record. A manager's answer is worth exactly what a customer's is.
Correcting: yes, but that detail is wrong
Use this when the work happened but the write-up is out by a fortnight or the figure is wrong. Before this existed, honest people had to confirm something false, decline into nothing, or close the tab.
You can correct three things and only these three: the date it was delivered, the amount, and what the work covered.
You cannot change the deadline, the title, or who the parties are. A third party rewriting those after the fact is a different agreement, not a correction.
Corrections only move one way. An amount can go down or stay the same. A date can move later or stay the same. Trying to raise the amount or pull the date earlier is refused on the spot, with the reason shown. That rule exists so the one door a stranger can reach cannot be used to manufacture better evidence for somebody.
What your correction does:
The date is the one detail written back onto the agreement. Whether the job counts as delivered on time follows from it, so correcting a date can move a record from on time to late. Say a corner shop's chiller was promised for the 9th and actually went in on the 23rd. Correcting the date is the honest answer, and it will show as late.
The amount does not overwrite theirs. Their figure stays on the agreement and yours is kept next to it, so both are readable. It is not ignored either: the outcome is reported using whichever of the two figures is the more conservative.
A change to what the work covered sits beside the record and is not used anywhere else.
A corrected confirmation counts exactly as much as an uncorrected one from the same person. It is not partial, downgraded or held back.
Declining
Declining is a full answer. It is not an accusation and it is not a complaint.
No event is reported to anyone's record under any decline reason, including "this did not happen". A decline is the absence of a confirmation, never a verdict against the person. The email Credda sends them says so in those terms.
On a delivery confirmation the reasons offered are:
This did not happen, or not the way it is described here
It may well have happened, but I cannot personally vouch for it
I am not the right person to ask about this
I do not recognize this work or the person who sent it
Another reason
A reason is optional and "prefer not to say" is the default. The person sees the reason you picked and anything you typed. It is never published on their public record.
Declining also stops the chasing for that record. If you were asked to vouch for something on someone's history, such as a job or a certificate, declining means that person cannot ask you again about that item at all, at any interval. They can name somebody else instead, which is the correct next move for them and is not aimed at you.
Ignoring
Nothing is ever auto-confirmed. There is no path in the product that turns silence into an outcome.
The record stays waiting. The link in your email works for 30 days, and the page tells you its own expiry, so believe the page over anything written here. You can be sent at most two follow-ups after the first ask, then nothing. How to stop Credda emailing you has the full limit.
What declining is not
Declining is not how you complain about work that went wrong. If a job was not delivered as agreed and you want that on the record, that is a dispute, it needs a Credda account, and it is decided from the recorded facts of the agreement rather than by a reviewer forming a view. Only a dispute that is upheld reaches a record. Declining alone leaves the work simply unconfirmed.