Algodoo

Check out my sedan... I figured it out, if you mean the "NaN" (aka infinity) that the k-probe outputs at around 0 rpm. for your display you generally want this as your input.

{scene.my.speed < 1000000000 ? {scene.my.rpm} : {0}}

for instance, you display would read

Text: {"" + {scene.my.speed < *0 ? {*1} : {*2} } }
*0: This needs to be way higher than possible, but less than infinity
*1: This will be your printed text value
*2: This is what displays if the reading from the k-probe is NaN

Is your simple if structure

Good Luck! Hope I answered your question... If you mean slowly moving numbers or rounded whole numbers I have no clue.