This timer only gets incremented by the main game ticker when the playsim is running.
This timer gets used for all playsim-related timing and animations so that these are decoupled from imprecisions in the global timer.
Currently the bit fields are still separate and they have to be merged, but for now the added memory does not matter.
Having this structure in the common parts will allow work on consolidating the input code, though.
Whatever this was for it made that thing extremely unwieldy.
With these merged the resulting structure doesn't look much different from Duke's anymore.