What happens to credits not spent after second First Choice round?

Been looking for this answer everywhere. Sorry.
Trying to figure out if we need to try to spend all the credits and when.

After the second round of FIRST Choice there’s an open first-come, first-serve ordering period until credits expire in April.

Here’s the KOP info page on FIRST Choice.

And here’s the flowchart for FIRST Choice.

First choice opens up to ‘normal’ ordering mode and your credits can be used to buy the remaining stock directly. (in past years anyways)