UCC28070: Question of the eqution53 at datasheet page36

Team,

May I check one UCC28070 equation with you?

For the equation53 at datasheet page36.

There should be –Vda2 instead of +Vda2 by letting current of Rta = current of Rsa.

Or could you help me to understand this if the answer is not what I think.

Thank you.