When I correct my tax credit to $1875 my tax refund actually refund increases by only $469. Any ideas as to why not $1875?

it may be a non refundable credit you are trying to add. Non-refundable credits serves to reduce your tax liability to "0" based off of your taxable income. Chances are your tax liability was only $469 before you applied that $1875 credit. When you applied the credit, only $469 could be claimed because that reduced your tax liability to "0" at this point. 

I spoke to someone at TurboTax and they informed me that I needed to leave the default credit at $7500 and not change it to $1875 as the program will do it automatically. What was happening is when I was changing the credit to $1875 the program was taking a percentage 25% it was lowering my refund to $469. (example- 7500 X 25% = 1875)