No limits – Exchange as much as you need, with full security.
It appears that there are various minimum limits but no maximum limits, so you're basically asking for trouble: e.g. Nothing stops users from placing orders above max supplies and that's going to cost you a lot of delays
[something that you're claiming it'd never happen (I'm not a developer by any means, but I don't think it'd be very hard to fetch a bunch of numbers from liquidity providers)].