Decimal after comma is not zero, the number is interpreted as 0,0

While designing a process that reads values from an Excel sheet, a PowerPoint file with embedded charts is opened by the process, and it iterates through all the charts and type in the corresponding values. These values are not correctly represented in the resulting graphs: If the decimal after comma is not 0 (e.g 6,1%), the number is interpreted as 0,0% (percentage is the number format in the embedded Charts). When using Math.Round on the number, the number is interpreted correctly but it loses the needed accuracy.

Change decimal symbol in Window regional settings. Use below link to change the separators.
https://professor-excel.com/change-thousands-decimal-separators/