BEARYBOW1972:
Good afternoon to you. First, I am not certain what it is you are baking. If you are baking a yeasted lean bread... then a cake of yeast is .625 of an oz or it is referred to as .6 of an oz. Simply put instant yeast would be 1/3rd that amount or 2 teasp. If you are going to use that junk that comes in a envelope & requires hot water to activate it then that packet is exact 1/4 oz...
use the whole thing. I hope this info will help you my friend. Good luck & have a nice day.
~Z~BESTUS.