If you're using the Receipts by Category summary report in the Transactions tab, you need to be aware that the calculations will be different between versions 3.1 and 3.5. This affects reporting for previous dates as well as future dates, because this is an interpolated report based on previous transactions.
These changes were necessary to correct some problems with the distribution of payments into categories. If you use numbers from this report for accounting outside of Campground Master, you should run a report for all prior dates and compare it with the numbers you used before, making any adjustments as needed. Otherwise when the reports are created for future dates, it could result in duplicate entries or missed entries, and possibly a completely different total due to errors in the previous reporting.