ROBLOX Sales Bugged?

I was looking through my sales and whatnot, and noticed that there were many instances where I was receiving less than I should have; my clothing is priced at 10 R$/item, item being a shirt or pair of pants, and for some of these, I’m only getting 6 R$ when I should be getting 7 since the tax is 30%. See below:

EXAMPLE:

OUTFIT ABOVE:

Any ideas why this is happening?