3 phase stepper with 1000 encoder

Hello,

I have a question that I cant seem to get my head around, would appreciate some help.

I have a 1.2 angle 3 phase stepper with 1000 line encoder. This means my motor does 300 steps for each full turn. However, if I understand correctly, the encoders line count of 1000, even though it becomes 4000 count, it can not be divided by 300, so...how does this work?

Btw, my drivers micro-stepping capabilities are 800, 1600, 3200, 6400, 12800, 25600, 51200,1000, 2000, 4000, 5000, 8000, 10000, 20000, 40000

Thanks.