robot trading


hi  iam using robot for trading

i would like to know the the trade size mathematic formula to hold a position down to 40 pip loss for usdjpy

stop out 50%

leverage 500

i thinks its like that

i have calculate this 40 pip of loss=400$ for usdjpy

for a balance of 600$

leverage 500

stop out 50%

so i think its 600$(balance)-400$(40 pip of sl)=200$

(600*105.331*500)/(105.331*100000)= 3 Lots

(400*105.331*500)/(105.331*100000)= 2 lots

so i think its 3 lots -2 lots= 1 lot of trading size to hold down to 40 pip of loss

but the suporrt of my broker say this

please try to understand, the maximum you can place 2 lots. and if you want to place 1 lot then your calculation is perfect.  

so iam little confused

thanks for  enlighten me