How to find Polarity and Start End point of transformer?
You define for them where you want the start and end pins. They will wind the transformer and connect the wires to the appropriate pins accordingly. 

It's one of those tedious things where you'd perhaps prefer to say 'whatever' and have them draw what they've decided and done, but as the commissioning designer, it's really down to you to choose the transformer pinout, and draw what you want.

You wouldn't go into a restaurant and say 'feed me'. You'd say 'I want the steak, bloody, with new potatoes'. Similarly they are waiting for you to draw a little insulating plate with 6 pins spaced 'yay' apart, labelled primary start, primary end, secondary ...