Is Kerabond T with additive okay for under Ditra Heat?

I'm looking to install porcelain tile over Ditra heat mat in our kitchen. From what I read you need to use a modified thinset for under the ditra mat(over plywood subfloor), and unmodified for over the ditra and under the porcelain tiles. I went to the local Lowe's and wasn't sure what to buy.

I'm not entirely sure what is what. I ended up buying Kerabond T - Medium-Bed and Thinset Tile Mortar and a jug of Keralastic.

Would this work if I added the Keralastic for under the ditra and don't add it for on top of ditra?

Thanks!