The mass differences you listed look like what could be expected over an infusion run; depending on the mass resolution chosen. You may need to export the list to Excel if you want to sum up the areas of the "different" masses.
The centroid option will only be available for an "advanced" user; just use the drop-down box to change from Standard.
There is probably a limit to how many it will list, although I think it must be very long, as I have had about 100 before now.
