The debug pie chart uses the OS locale specific number formatting, for example for German this means a comma (,) is used to separate the integer part of a number from the decimal part.
- Change the locale setting in your OS to for example German
- Open Minecraft
- Display the debug pie chart by pressing SHIFT + F3
Based on 1.12.2 decompiled using MCP 9.40
A java.text.DecimalFormat object using the default locale is assigned to net.minecraft.client.Minecraft.displayDebugInfo(long).decimalformat.