When I enter my first charitable donation amount, it is calculating a 25% credit instead of the 50% that it should. Why would one be different?

The credit given for donations is based on the total amount of donations you're claiming in the year. For example, if your total donations were $200, you'll receive a credit of 15% or $30. If your total donations were $1200, the credit for the amount above the $200 figure is higher. 

$1200 donation = $320 credit

• First $200 = $30 credit ($200 X 15%)
• Remaining $1000 = $290 credit ($1000 X 29%)

Please note that the First-time Donor's Super Credit was retired in 2017.