Actually what you have is the molecular weight. Do not worry so much about the z part of m/z values. It is too small a quantity

There are a couple of things that are not clear here. How can you have a chromatogram that shows m/z in it? Do you mean total-ion chromatogram? (that's a bit of a misnomer, by the way) You probably have a spectrum where the oligosaccharides appear as several peaks, at different m/z values, due to multiple charges. Which immediately invalidates the above answer: if you have a mass of 100 and a charge of 1, you will see that ion at m/z 100, but if the charge is 2, you will see a peak at m/z 50 also, so worry very very much about your charge, because in your case it may show peaks at hundreds of Daltons mass difference, which are nonetheless related (originate from the same species). Here is a simple tutorial that helps you learn how to determine the multiplicity of the charge and hence the molecular mass (MS does not deal in weights): http://www.ionsource.com/tutorial/spectut/spec5.htm

Julius, I feel she is getting this m/z values from mass spectrography results.