Can anyone explain what the temperature measurement frequently paired with an ISO rating means? For instance, I have a box of HP-5+ here that says it's "ISO 400/27 degrees". Some Fuji Pro 160S says ISO 160/23 degrees. Should I be altering my film speed for ambient temperature? Temperature is on my mind since getting a Jobo - I have to use ice baths to get the water bath (filled with cold tap water) down to 75F for b+w developing.