Zeroing Mitutoyo Digimatic Bore Gage

I have picked up a Mitutoyo Digimatic Bore Gage. It is the model that will accept 2 sets of anvils. This gage will accept 2.4-2.8in or
2.8-3.2in. It only came with the 2.8-3.2 range anvils.
This is the "digimatic" type that has revolving numbers to read the measurment. It has a screw at the bottom of the shaft that will allow you to rotate the viewing window, but the problem is that the thousandths and tenths zero line move together when the window is moved. I need to keep the tenths stationary and move the thousandths to get this zeroed with a ring gage.
It did not come with any literature. Anyone have any idea how to zero this bore gage?
Thanks, Steve
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