You now need to enter a timeframe when making a sign (on the 3rd line) such as Recent, Week or Month. The recent timeframe will show the most X most recent payment, the week and month will show the X top donor from that timeframe.
The plugin will now get all payments (Limited by the cache amount in the config) and add them up to work out the top donors in the last week and month. If you get more payments than the cache amount in your config in a week or month (Depending on what you use) you may need to raise the cache amount.