If you accounted for atmospheric pressure it should be good. Light syrup is common on a first run, you should have your highest sugar content in the first few weeks of sap collection. The complex nature of syrup colour, taste, clarity from batch to batch are incredible....search it on this site when you want some light reading material ;-)
Try this App the next time you finish a batch: https://www.saptapapps.com/ it saves boiling water for an hr while getting your thermometer calibrated.
I bring mine over temp (thicker than syrup) in the evaporator, let it settle for a week, decant it into my finishing pot, bring it to temp and thin it out until the specific gravity is spot on, then bottle. Way faster during finish.
2014 - 6 buckets, 4 coffee cans and a propane burner - almost 40L of sap and 1.6L of syrup
2015 - 103 taps on gravity. Homemade oil tank arch and a Smoky Lake 2' X 5' hybrid. - 2.66 gallons of syrup
2016 - 101 taps, 550 gallons of sap, ~10 gallons of syrup all dark.
2017 - 138 taps, 225 gallons of sap, 5.55 gallons of dark syrup, still procrastinating on the vac.
2018 - ~150 taps, I lost track of the sap it was incredible!, over 20 gal of syrup, all dark.