Gain and offset

Good day!
I’m trying to do radiometric calibration in ENVI. I saved cropped S3L1 images in netcdf4. Now ENVI asks me to provide gain and offset for a band.
Where can I find it?

I tried ./Bands/frame_offset but it did not work.

Thank you

Select the band in SNAP and then chose from the menu Analysis / Information.

Thank you!

Can I find it somewhere in .nc files (metadata or something else) if i want to open them not in SNAP?

Yes, it is in the variable attributes of the NetCDF as scale_factor and add_offset.
See the product format specification. Here for OLCI:

Thank you, Marco. We’ll see