Hello from Engineering team.. I investigated this and actually do not see any reason why this is not allowed. I think any things should be allowed in the input area. I will do some basic testing after removing this restriction. If every thing works will ship it.
Please fix this. Having to write out "percent" or "greater than or equal to" instead of "%" and ">=" takes up a lot of space, not to mention having to put a letter in front of the actual message "z 89-70" so it can just say "89-70" is silly.