1) To adjust it on the panel, use the fine adjustment (FINE).
The setting resolution of FINE is as follows:

When OUTPUT is OFF:
• L type: 10 mV
• ML type: 10 mV
• MH type: 100 mV
• H type: 100 mV

When OUTPUT is ON:
• L type: 1 mV
• ML type: 1 mV
• MH type: 10 mV
• H type: 10 mV

2) It is 0.1 mV for all models via the communication interface.

For the details, read the user’s manual – chapter of Specifications.