What do professional pilots keep track of in their pilot log books?
The experience required is simply flying hours on the type or configuration, and flying hours, for pilot logging purposes, is time from engine start to engine shutdown.  If you're flying an airplane with a Hobbs, which usually starts/stops using oil pressure, you can just use the Hobbs value.  If no Hobbs, record the engine start/stop time yourself and use that, or if you forgot to, just use the tachometer hours reading (which is closer to air time, or time airborne) and add a 10th.