Hi Monica,
Yes there is a way to do this. I am not sure I fully understand what you mean how it doubles the quantity available, because you enter the quantities of each style manually, and therefore it shouldn't double those. I just ran a test under the Men's accessories>Ties category and was able to set the quantites and so far they're all staying where I set them for each style. Maybe if you could reply back and let me know where it's doubling the quantities I could try and find the culprit. Thanks!