if your ticket is BLR-DXB-JFK, you will be fine; piece concept will apply. you should be entitled to 2 x 23kg, however, for a fee, i think, of $50 per piece, you can increase the allowance to 32kg. no luggage over 32kg will be accepted at BLR or JFK, especially because of strict DXB baggage movement rules, etc.

the 20kg appears because if you book BLR-DXB-BLR, weight concept would apply with 20kg in Y, 30kg in J and 40kg in F.

but dont worry, you appear to be entitled to piece concept anyways!

-t.