Why is the dividend tax credit used in the calculation different than the amount I provided fromn T5? How do I check the credit calculation on a T1 condensed?

Credit calculation is not available to see on T1C .  you can calculate it using information at  https://www.taxtips.ca/dtc/smallbusdtc.htm

It should match what is reported on T5. The reason it can be different is if you are preparing joint return and your T5 income is split with the spouse ( or another beneficiary on the account)