Has been suggested to me to use a yeast calculator which I've downloaded , I understand most of it , temp, type of brew, original gravity etc but asks for viability expressed as a percentage , I really have not a clue what that is , it shows 90% as a start figure if that helps at all. Doing lager kits just at the present and some wine kits , not progressed to mashing yet, but if I can improve kits by having more accurate yeast pitches would be a great step in the wright direction .