Paid ct state tax at a rate of 5.5% and turbo tax indicates 5.1% income for credit to Mass not 5.5% is that right?

It's correct.  MA's 2018 tax rate is 5.1%.  You can't receive an out-of-state credit that's greater than your own home state's tax. 

In other words, if you paid CT $1,000, and your MA tax bill is $800, the most you can take as an out-of-state credit is $800.  MA isn't going to pay you an extra $200.