A couple factors can influence that. First would be making sure that all that apps that queue a given agent are included on the Canvas. The other would be checking with Producer to see what refresh rate the canvas is set at. If it's slower (say 9 seconds) it might not match up too often, depending on call volume. The teleset display updates instantly.
Are you using one of the pre-built Aspect canvases, or custom built one? Also, what kind of discrepancies are you looking at?