2.S.
When listing in lots, I make sure I list only 1 size. So if I have girls shirts in 4T and 5T I will sell 2 separate lots, one all 4T the other all 5T. And in my listing I will add something like, please check out my other auctions more more girls size clothing in size 5T, 6T, etc...
Best of luck on selling!
I have been selling on eBay since 2003