I am using this formula to find the equilibrium conc of Fe3+

[Fe3+]eq = [Fe3+]Initial - [FeSCN2+]eq

Now my question is, for the initial Fe conc, do I use the concentration that is stated on the bottle? (Bottle that the Fe came from which was 0.150M) Or should I multiply that concentration by the amount used (5ML) and then divide by total volume of solution 25ml (5ml fe, 10ml scn and 10 ml HNO3)