Hopshot is sold in 5 ml syringes. Each syringe provides 50 ibu for 5 gallons of 1.050 wort boiled for 60 minutes. As the wort gets above 1.080, utilization decreases.
Here is a chart:http://www.northernbrewer.com/documentation/hopshot.pdf
So for a mid-1.070ish beer you're looking right at or just below 100 ibu. But NB also reports that test batches show perceived bitterness is less aggressive with hopshot.
I think what you're seeing in that recipe is an even two hopshots being added in their entirety (easier) with ibu calculations from Beersmith or similar. In reality it's probably closer to 90 ibu, but again, I don't think you can perceive the difference between that and ~75.
If I'm brewing that particular recipe as written but didn't have access to hopshot, I would toss in an ounce of either Warrior or Apollo (assuming 15%+ AA) at the beginning of the boil.
Hope that helps.