Each offer includes a goal table, which lists all the possible compensated goals for that offer.
Normally, a goal in an offer will be confirmed within a few minutes. However, it can sometimes take a few hours or even up to 48 hours.
When a goal has not yet been confirmed, a spinning circle will appear next to it in the goal table:
As long as this spinning circle is visible, the goal has not been confirmed. Once the goal is confirmed, a checkmark will appear in its place:
If you have already achieved a goal in the game, but it has not yet been confirmed in the goal table, there could be several reasons why the checkmark has not appeared.
Additionally, most offers have a specific time limit within which you can test the offer. Check out the test limit in the respective offer's description.