Tappet Clearance

I have an old Motor's Truck repair manual that gives tappet clearance for "Running Hot" and "Timing"
Can anyone explain the "Timing" part.
For the Green Diamond it shows 0.0015" for intake and exhaust running hot, then 0.0020" for timing.
Maybe to check the valve timing the clearance needs to first be set at 0.0020"?

I think it is the "Cold" setting, if you were building an engine and wanted to check or adjust the the valve timing, you can't get the valves and engine hot, to get an accurate read on what the valves will be doing in a hot, running engine, so the cold setting is an aprox.
By the way the clearance is .015 and .020 not .0015 and .0020

Thanks for the reply. Your explanation makes sense.
Yeah typo, I did mean 0.015 and 0.020.