It will work with -ve angles IF the attribute like “RotZ” is included in proper “double-quotes”.
If you read what you have typed in the formula…
It WILL fail because you have typed in something else !
If you typed it as I showed, with “” around the RotZ it works just fine !
ANIMATE("RotZ", 0, -90)
You seem to be typing in some kind of ‘smart-quotes’ - so you need to reset some typing system-preferences somewhere [MAC? See here Welcome macissues.com - BlueHost.com ] - ordinary “double-quotes” are ALWAYS needed in DC formulas which require them…
AND ALSO rotating by 270 is NOT the same as rotating by -90, because the swept arc is bigger x3 !