Ca 4liter förlust i mäskningen. 20 liter blev ungefär 16 liter till koket. Ca 2 liter a kok.
Based on boiling 16.00 gallonsliters at 1.068 for 60 minutes, this will decrease your wort by 1.00 gallonsliters, bringing your after boil OG to 1.072. You wanted an OG of 1.073. It looks like it will be under.