Hi Annina,
Hope everything goes well with you. With the latest release of our app, you will now be able to configure the display format/pattern of numbers in the legend and hover texts of your pie chart. In your case, if you want to round the decimal number, you can input "#" into the Pattern box. If you want, you can control the number of decimal places by adding more "#" e.g. "#.#" for one decimal place, "#.##" for two decimal places, and so on.
If you need any further help, please let us know.
Thanks
Tif
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(As shown below, you can find the setting at the bottom of the Chart tab.)