3 vessel E-HERMS system, I use Brewer's Friend for calculations, just brewed a saison and my OG is lower than expected. According to the software, I was hitting all of my numbers spot on, including the pre-boil gravity of 1.044 in 7 gal of wort, and I took a couple measurements just to be sure. I use a steam condenser, so my boil off is pretty low, but according to the software boiling for 90 minutes should get me down to 6 gal, with a gravity of 1.051. 90 min later I am exactly at 6 gal, but after cooling and taking a measurement, OG is 1.042. Boiling longer would bring this down, but I am just confused as to why after 90 minutes of boiling and reduction of wort, I end up with a gravity lower than the pre-boil. I measured with two different hydrometers, and a refractometer, all show the same number in both pre-boil and post. Thoughts?

Here's the recipe:

Boil Time: 90 min

Batch Size: 5.5 gallons (fermentor volume)

Boil Size: 7.01 gallons

Boil Gravity: 1.044

Efficiency: 76% (brew house)

Hop Utilization Multiplier: 1

STATS:

Original Gravity: 1.051

Final Gravity: 1.004

ABV (standard): 6.2%

IBU (rager): 36.23

SRM (morey): 3.26

Mash pH: 5.66

FERMENTABLES:

7 lb - Belgian Pilsner Malt (70%)

3 lb - Spelt Malt (30%)

HOPS:

0.85 oz - Styrian Goldings, Type: Pellet, AA: 5.5, Use: Boil for 60 min, IBU: 19.62

1.15 oz - Styrian Goldings, Type: Pellet, AA: 5.5, Use: Boil for 30 min, IBU: 14.74

0.5 oz - Styrian Goldings, Type: Pellet, AA: 5.5, Use: Boil for 5 min, IBU: 1.87

OTHER INGREDIENTS:

6 g - Gypsum, Time: 60 min, Type: Water Agt, Use: Mash

YEAST:

Fermentis / Safale - Belgian Saison Ale Yeast BE-134