Quantity Difference while convereting TR/TO

Hi Expert,

I'm facing a quantity difference issue while system automatically convert transfer requirement into transfer order in background. I posted a good receipt of material 27589 in 3 batches as AA 20 qty, AB 15 qty and AC 30 qty. TR was created with AA 20 qty, AB 15 qty and AC 30 qty but TO was created with as AA 20, AB 10 and AC 30 qty. There was difference of 5 qty for batch AB..Can anyone let me know what the reason is behind?

Regards

Mihir