Why is there this difference in the values ​​shown for the used disk space between df and duf ?

[insinfo]

Why is there this difference in the values ​​shown for the used disk space between df -h and duf ?

isaque@pmro174330:/mnt/c/MyDartProjects/new_sali/backend$ dart ./bin/experimentos/get_linux_process_info.dart
statvfsFunc total: 250.98248672485352
statvfsFunc disponivel: 246.54766082763672
statvfsFunc used: 4.434825897216797
statvfsFunc usedPercentage: 1.7669861969606657%
main DiskInfo(total:269490393088,available:264728535040, used:4761858048, usedPercentage:1.7669861969606657)
process_cpu_seconds_total: -1.0
process_start_time_seconds dart: 1698431675.996
process_start_time_seconds: -1
process_virtual_memory_bytes: -1
process_working_set_bytes: -1
process_private_memory_bytes: -1
process_num_threads: -1
process_open_handles: -1
isaque@pmro174330:/mnt/c/MyDartProjects/new_sali/backend$ df -h /
Filesystem      Size  Used Avail Use% Mounted on
/dev/sdc        251G  4,5G  234G   2% /
isaque@pmro174330:/mnt/c/MyDartProjects/new_sali/backend$ duf /
╭─────────────────────────────────────────────────────────────────────────────────────────╮
│ 1 local device                                                                          │
├────────────┬────────┬──────┬────────┬───────────────────────────────┬──────┬────────────┤
│ MOUNTED ON │   SIZE │ USED │  AVAIL │              USE%             │ TYPE │ FILESYSTEM │
├────────────┼────────┼──────┼────────┼───────────────────────────────┼──────┼────────────┤
│ /          │ 251.0G │ 4.4G │ 233.7G │ [....................]   1.8% │ ext4 │ /dev/sdc   │
╰────────────┴────────┴──────┴────────┴───────────────────────────────┴──────┴────────────╯
isaque@pmro174330:/mnt/c/MyDartProjects/new_sali/backend$ /mnt/c/MyRustProjects/rust-df/target/release/rdf
Filesystem  Size  Used Avail  Use%                      Mounted on
/dev/sdc  251G   17G  234G   6.9 ■■■■■■■■■■■■■■■■■■■■ /
none        4G   22M    4G   0.6 ■■■■■■■■■■■■■■■■■■■■ /mnt/wslg
tools     476G  397G   78G  83.5 ■■■■■■■■■■■■■■■■■■■■ /init
isaque@pmro174330:/mnt/c/MyDartProjects/new_sali/backend$