A first step for the troubleshooting would be the output from the special agent.
You can find this data inside “~/tmp/check_mk/cache/hostname”
There you should find some lines like the following.
localCapacityBytes 75952808613643
localDiskBytes 22344832993627
localFreeBytes 50913720534795
localUserBytes 82628407208398
combinedCapacityBytes 75952808613643
combinedDiskBytes 22344832993627
combinedFreeBytes 50913720534795
combinedUserBytes 82628407208398
My system has 70TB and the value is correct there.
As i have no cloud storage, booth values local and combined are identical.
Can you have a look your data?