In our exchange we use a shared wallet model, meaning that all users are depositing in the same wallet. This is standard practice for all centralized exchanges. When you send coins to the deposit address assigned to you, those coins are pooled with other users' deposits and we credit that balance in your account. Afterward, all the movements in your account happen "off-chain". For example, if you sell those coins, there won't be a blockchain movement for that. We will only move those coins when someone else needs them, for example, a withdrawal.

The problem is that moving those coins has a cost. This cost is usually fixed, meaning that a small deposit is worse than a large deposit. For some platforms (e.g. Ethereum) small deposits are even worse because transactions are limited to one source one destination, so coins need to be consolidated first before moving them to the final destination.

In the vast majority of cases, we cover this cost ourselves, but we ask users to send deposits that are larger than a given amount. The more expensive it is to move a particular type of coin, the larger this minimum is for that coin.

Since blockchain payments are passive from the receiver side (except for Lightning Network), there is no way we can reject your payments if they are too low. In other words, we can't prevent a payment from arriving at our wallet even if that payment will be problematic for us. For this reason, if you breach our agreement and you send a deposit that is lower than what we indicated, then that deposit will not be credited and will be used to cover the expenses of moving those coins.