Higher KW on the secondary winding of a transformer
I think the 3-phase input complicates things so the calculation is not the same as for a "normal" (1 phase) transformer.

There's a calculator and some formulas here

If I fill in:

Three phase
P = 4.8 kVA

Line to line voltage = 208 V

then I get the 13.3 A

BUT if I select:

Line to neutral voltage = 208 V

I get 7.7 A

So it depends on how you connect the loads to the transformer, see Three-phase power.

Also this might also help you understand.