After thinking about it more, I think one of the issues here is the way the output of df is being parsed. When I run df, the output contains a newline. The regex used to parse splits on spaces. Here is the output from df on my system:
actual:/var/local/vps-bu# df /mnt/compvps/vz/private/108/
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/actual--vg001-vps--storage
100756920 6411820 89226944 7% /mnt/compvps
The output of lvscan may also be helpful:
actual:/var/local/vps-bu# lvscan
ACTIVE '/dev/actual-vg001/vps-storage' [97.62 GB] inherit
ACTIVE '/dev/VG-RAID/LV1' [144.35 GB] inherit