Consider this problem: you may be trading in 100 different symbols, and all with different quantities. You can specify the quantity here in APIBridge->Symbol Setting.
Firstly if you want to scale-in to positions, it will be difficult to code all quantities in your strategy program such as Amibroker or MT4.
Secondly, same goes for scale-out also, if you want to exit (say) 40% of all net positions, in that case it will be difficult to code for all different quantities.

So In that case the problem amplifies if you are trading in multi-client accounts.

In that case to solve this problem, we have additional hack in Signal protocol call Qty Multiplier. Moreover before reading further, you should be thorough in coding Signal for all available parameters.

Qty multiplier for LE/SE/LX/SX

In the signal:
ID,Type,Symbol,OrderType,TrigPrice,Price,Qty,InstrumentName,StrategyTag

Qty can also be given as Qty|EntryQtyMultiplier|ExitQtyMultiplier

Final qty for order placeemnt for LE/SE= int(Qty(from signal/ui) * EntryQtyMultiplier)
Final qty for order placeemnt for LX/SX= int(NetPos * ExitQtyMultiplier); where ExitQtyMultiplier = Min(1, ExitQtyMultiplier)

Scale-in Example:
AlgoJi_Signal(“1”, “LE”,”AA”,”L|NRML”,””,”305″,”100|3″,”EQ”,”STG1″);
In case In symbol settings assume qty is null
Qty for order placement = int(100*3) = 300

Scale-out AlgoJi_Signal(“1”, “LX”,”AA”,”L|NRML”,””,”305″,”100|1|0.5″,”EQ”,”STG1″);
NetPos=200
Qty for order placement = int(200 *0.5) = 100