Sidebearing formula for width and SB

For my j, I want the RSB to be identical to the i and the width also to be identical to the i. So, I entered “i” in the “W” and “R” fields.

This leads to a strange behaviour: If I click the circle-arrow for either then the other one turns red. I can do this back-and-forth as many times as I want.

Instead, it would be practical (and logical) to calculate the LSB automatically to satisfy the other two conditions.

This is what it should do...