How to read Ultra Gauge fuel trim data?

[oldtamiyaphile]

I started trying the read my Fiat's fuel trims and have found the following:

Short term trim tends to jump from (roughly) -100 to plus 90 with even the slightest movement of the throttle.

Long Term trim does much the same, it looks like an instantaneous readout.

I've been using the O2 sensors as a more readable way to extrapolate AFR's.