To calibrate your meter for the LA-610 follow the steps below.

1) Turn the LA-610 on and warm up for appx. 5 minutes.
2) Turn the GAIN knob to 0
3) Turn the Compressor section (right side) Peak Reduction control full off.
4) Adjust the GR Zero Set trim pot so the meter reads 0 dB.
This is the small screw found directly underneath the UA logo, on the right side beneath the Meter window. Turn this small knob until the meter reads 0 db.

These steps can also be found on page 6 of the LA-610 manual.