There are different standards for "10% solution": it can mean weight per weight, or it can mean weight per volume. The former would mean 100g KBr plus 900 g water as stated by dEfENDER, the latter would mean 100g dissolved in enough water to make 1000 ml. Both versions are common and, sadly, few formulas state which one is meant.
Since at concentrations at or below 10% density of liquids is reasonably close to 1.0, and since your application doesn't appear to demand high accuracy, there is little difference between these standards for your case. Therefore you can state with sufficient accuracy, that 2ml of 10% KBr solution contain 0.2 g KBr.