> I tried running it in MPLAB's debugger, but the debugger runs
> straight through the code, from top to bottom, and seems to be
> ignoring any and all CALLs and GOTOs that are placed in it.

Seems OK here

> The watchlist updates none of the defined variables (EQUs)
> that I can tell.

At 4MHz, INCFSZ Rghtdsp is reached after 2.1 seconds and Watch
shows the increment

Just a few tips to make the code more readable (re note yesterday
about labels being comments too)

#define ones          porta,0
#define tens           porta,1
#define hundreds  porta,2

and use eg BSF ONES instead of BSF PORTA,0

RAM definitions are correct for the F628 but may not be for
other micros. CBLOCK is easier to use for absolute addressing

    CBLOCK 0X20  ;note only base address needs to be changed

    RghtDsp      ;no addressing needed here, typos avoided
    LeftDsp
    CountW
    etc

    ENDC

but you should be looking at relocatable code

Also, at least use CLRF STATUS at the start to make sure RP0
and RP1 are 0 (bank0 is selected)

Default register is F so ,F is not needed after instructions. Saves
a little clutter. And makes it easier to spot ,W mistakes

Resetting variables to 00 is a good habit. I've been caught by
that. CLRF variable is another clutter-saver

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