Hello i am tryng to calculate duration values ,for bmw 525d 120kw ,but i have a problem with engine rpm becouse in duration map x axis is mm3 i converted it to mg/str

Y axis is rail pressure in hpa and map is in microseconds uS ,and lets say we take 35mg/str at 1000bar we have 844uS but at what rpm ,its becouse more rpm les time you have to inject ,so i dont get it how to calculate duration when i dont know rpm ???

I found rail pressure map but there is olso problem to me i have rpm pressure and IQ but how to now time ?