Casio PRO fx-1 Indirect Help?

[toml_12953]

I'm trying to wrap my head around how the Casio Pro fx-1 uses the indirect register, I. I tried the program below which I believed should display 10 in register 1. It doesn't.

Code:

MAC:
I=K5:                  // RI = 5
5=K2:                 // R5 = 2
2=K10:               // R2 = 10
1=I:                 // R1 = RI
ANS 1:             // Display R1
5:                    // Display R5
2:                    // Display R2