Pre boil gravity 1.059 15 brix Original gravity 1.087 23 brix Final gravity 1.015 ABV 9.6%
Based on boiling 8.00 gallonsliters at 1.059 for 90 minutes, this will decrease your wort by 1.50 gallonsliters, bringing your after boil OG to 1.070. You wanted an OG of 1.091. It looks like it will be under.