Hmmm... Should have a minimum 1%, I suppose. Dexterity/300 is correct - for instance, with 30 Dexterity, you would have a 30/300 or 1/10 chance each time you tried. To have 0% your Dexterity must have been lower than 3, at least at the current time. Was that the case? And/or did you have Tsunami Fever (halving your current Dexterity) or Clumsiness (temporarily halving your Dexterity) or both?