Chart not showing same data as report

We have a report that shows all sector activity by month. I decided to create a bar chart illustrating this data; however, the numbers don't match up. For example, in January, there were 51 total activities (25 meetings and 26 calls). The chart, however, shows 55 total activities with 41 meetings and 24 calls - all of these numbers are off (not to mention 41 + 24 does not equal 55 total activities). What am I doing wrong here?
Thanks,
Colin