System Monitor

Hi, I have a RPI 4 8Gb where is installed Home Assistant Core in a docker.
i have an usb drive connected on, but there is no way to monitor the disk use for this usb disk.
I can monitor the disk use where Raspian in installed but nothing to do for the usb disk connected.
The device is:

File system Dim. Usati Dispon. Uso% Montato su

/dev/sdb2 932G 73G 859G 8% /media/pi/Share

Do you have any suggestion to revolve this issue?
Thank you.