FS space commands returns wrong values

$rm(fstot, int) returns 10690 Mb, bit I have 16 Gb internal space. The other FS commands alsó returns wrong values

The function "fstot" returns the total filesystem allocated, you might have more but thats what it has been allocated to filesystems, maybe 4/5gb are not mounted or used as swap devices, these are not considered in the total.