Everywhere i look it says to add bac to hcg to mix and then your dosage is the amount of hcg divided by the amount of bac you added. My question is what about the displacement from the powder? Wouldnt there be slightly more volume so for example:

"Most common will come in 5000 IU
Say you add 1ML of BW that will leave you with
5000 IU/1mL:
50 IU per IU(1 mark on slin)
500 IU per 10IU(10 mark on slin)"

My point is here if theres more volume than you account for then your gonna get less hcg than you think your getting. Ive never done this and am a noob so What am i missing?