Is the Dependent Care Credit calculation only for those that don't fully utilize a FSA? I'm confused when both expenses & Credit amounts were subtracted by FSA amount.

It depends. 

The maximum "qualifying child care expenses" allowed for the Child and Dependent Care Credit is $3,000 for one child, or $6,000 for 2 or more children.

If you contribute the maximum $5,000 to a FSA, you are not eligible for the Child and Dependent Care Credit if you only have 1 child.  

However, if you have 2 or more children, and contributed $5,000 to a FSA, you can still take the Child and Dependent Care Credit on expenses up to $1,000 of qualified expenses.

See the TurboTax FAQ for more details about getting the Child Care Credit below:

https://ttlc.intuit.com/replies/4395614