I think it’s 8 seasons in US, depending on what series of CSI.
But as stated in above post all 16 seasons are not available on demand to be downloaded from Pluto.
They may show seasons or episodes above 8 but that is the TV part of Pluto which SF can’t download.
If you need them bad enough try researching record software and record from the TV section of Pluto.
But it may end up either tedious or the record software may not even get them all.
You could try justwatch or simular to search for places that might have more, but more then likely no service has all seasons available.
