Here are the instructions, directly from the manufacturer:
Please read the instructions before you begin the test and be sure that you understand how to take your sample, place test stick in the test tube for no less than 20 minutes and no more than 40 minutes before you read the test.
If you read the test more than 40 minutes after the test stick was placed in the vial, the result of the test is not valid. Do not consider the result an indication of your HIV status.
You spend a lot of time reading things that aren't useful on the internet. Testing is accurate for true risks and you can know in as little as 28 days post exposure (that is actually a risk) if you contracted hiv. What was the exposure you are referring to.