Oh sure! If there were two chlorines present in the chemical, then any fragments in the mass spec that contained 2 chlorines would appear as a triplet of peaks, 2 mass units apart, in the ratio 0.578:0.365:0.058 (if I did the math correctly, 0.76x0.76:2x0.76x0.24:0.24:0.24). So it would be easy to distinguish between fragments with one chlorine or with two chlorines: the characteristic triplet would mean 2 chlorines and the doublet would mean one.