It's astonishing to me how this is so confusing. A substantial amount of money you earn goes to paying taxes... shouldn't everyone have a basic understanding of how this works??
Maybe this is a better way to put it: As long as the total income tax you have to pay FOR THE YEAR is more than $3750, you will get the full credit.
Think of it as having a coupon for $20 off your next purchase at a store. If you go buy something for $15 the store doesn't give you the extra $5. The $3750 is like having a coupon for your taxes. If your total income tax you owe for the year is less than the coupon, you only get the smaller amount.
I think people think that what they have to pay/get back on April 15th every year is their tax or something.