Ouch.

Quote
Trade size given by an integer number of lots (default = 1; max = LotLimit). [...] Since it's the minimum, the trade size can never be less than 1 lot (see remarks). [...].


I am coming from the MT4 world, where Lots can be "microlot". The reason I could not close partially by modifying TradeLots is because I tried to change to 0.5. For further readers: also check the Hedge mode.