Series Six program conversion

I am converting a series six program over to a 90-30
with a 350 cpu using Cimplicity ME ladder logic. While perusing the old program, I found something unexpected in the way the engineer used a certain register.
Here's the logic:

First rung
Reg984 Move Reg 985 (move the contents of register 984 to reg 985
2nd rung
10*reg990=reg985 (multiply 10 times register990 with the
answer going into register 985)
3rd rung
reg985*reg1005=reg985 (multiply register985 times register 989
with the answer going into register 985)

I guess I don't completely understand how the old dinosaur executed the program but it appears that register 985 would be unstable for use as a final control element. I converted the program to Cimplicity and it accepted it but I got a "warning 8022 type mismatch between variable and instruction"
Should I create new registers to prevent a problem?
Thanks in advance

Your text description doesn't exactly match your pseudo-graphics. If you can make a printout of the LM6 rungs to a .txt file and post it here, I'll be happy to take a look at it.

If you're willing, zip up the entire file and post it. You should zip the .lad, .nam, and .exp files for the job from the LM6 directory.

It looks like R985 is being used as a 'scratchpad'. By that I mean it's just a holding place for intermediate values.

The program looks like it's for a hydroelectric station. Was it originally done by Phoenix Controls?

So you mean the series six will just refresh the value of R985 each place it is used in the program? It is difficult to get anything from Fanuc about exactly how the program gets executed.
Yes, this is a hydro and this register helps set the pulse length
and time between pulses for the gates that spill excess water and the pulses for the gates that regulate the flow into the turbines.
Phoenix did not do this plant for us but they did a couple others for us. The engineers name was Steve Baughn(sp?)I think Phoenix got bought by ABB.