You can find the VDSL Diagnostics at Diagnostics → VDSL.
Here you can see the current settings and status of your VDSL setup.
To change your VDSL setup please go to Interfaces → Assign → VDSL and refer to the documentation at VDSL.
Status shows you the current status of the VDSL modems. Possible values are READY, HANDSHAKE, TRAINING and UP
Mode shows you the connection mode once a connections is established with the DSLAM. Possible values are VDSL and ADSL
Upstream is the upload speed
Downstream is the download speed