Learning Magic

Ok, so this is what I have so far... I think I need a little help understanding the accumulator and RAM operations.

Code:

C3/50A2:    85E0        STA $E0
C3/50A4:    20DD4E      JSR $4EDD
C3/50A7:    B90000      LDA $0000,Y
----------this is where my code starts-------------------------
C3/50AA:   8D0442      STA $4204  (Divider A)
C3/50AD:   A90C         LDA #$0C (12)
C3/50AF:   8D0542      STA $4205  (Divider B)
C3/50B2:   AD1642      LDA 4216    (MathValue Math coprocessor's result. Remainder for Divisions)
----------this is where my code ends-------------------------
C3/50XX:    8D0242      STA $4202
C3/50XX:    A936        LDA #$36
C3/50XX:    8D0342      STA $4203
C3/50XX:    7B          TDC
C3/50XX:    A5E0        LDA $E0
C3/50XX:    C220        REP #$20      (16 bit memory/accum.)
C3/50XX:    6D1642      ADC $4216
C3/50XX:    AA          TAX
C3/50XX:    E220        SEP #$20      (8 bit memory/accum.)
C3/50XX:    BD6E1A      LDA $1A6E,X
C3/50XX:    60          RTS

**I am overwriting Gogo's code, its not going to get used anyway.**

So what I am expecting to happen is for it to use the remainder of the actor/12 (#$0C) to determine what spell to look at, not the raw actor number. The result I am actually getting is all of my actors are seeing the same random magic percentages, when I scroll down the list in the menu and come back up, some of the values disappear, while others change value.

I'm still new to assembly code and I think I have some fundamental misunderstanding of the registers, accumulator, and RAM. Since the values change when I move around, does that mean the numbers aren't staying consistent in the accumulator, if so, why would that be? Also, $4216 in the RAM is used for both the product of multipliers and the remainder from division... this code uses both, so if I have values in $4202, $4203, $4204, and $4205; what number would I expect to see in $4216? And finally, what is the difference between "MathValue" and "MathValue!" ?