Sentinel Hub convertion from 0-255 to reflectance values

I suggest you check these links:
https://www.sentinel-hub.com/faq/how-do-i-get-actual-ndvi-values
https://www.sentinel-hub.com/faq/how-are-values-calculated-within-sentinel-hub-and-how-are-they-returned-output
https://docs.sentinel-hub.com/api/latest/#/data/Examples_for_S2L2A

Thank you that’s great., I’m writing the script in sentinel hub and i need also to read the NDVI value in arcgis or qgis the values is steal in RGB band.