Boiled off to 4.5 gallons to the fermenter @ 1.063. Diluted with 2.5 Q of sanitized filtered water to bring back to 1.056
Based on boiling 7.50 gallonsliters at 1.045 for 90 minutes, this will decrease your wort by 1.50 gallonsliters, bringing your after boil OG to 1.054. You wanted an OG of 1.051. It looks like it will be over.