IDEX – fewer tokens after MM withdrawal?

Hello all. Bit of a question.

I've recently made a withdrawal from IDEX to Metamask, and the amount of tokens received into MM is a bit lower than what I took out from IDEX. Example:

Tokens bought: 107 (all good)

Fee: 107-0.001% = 106.893 (this is the amount in my IDEX balance; all good)

Withdraw to MM: 106.893.

But now I noticed that on MM as well as the MM address on Etherscan, there's 106.72.

Am I missing something?