HP is the same, BHP is measured before drivetrain loss (brake horsepower measured at the flywheel), WHP is measured after drivetrain loss (wheel horsepower measured at the wheels).
The peak HP gain of the device is 22 hp, the 38 number is max gain (where the biggest difference between the curves is).
To compare this roughly to Cobb tunes (according to the claimed percent increases in their map notes), assuming a general stock Fiesta ST is at 185 whp:
Peak 2% gain (3.7 hp)
Max 5% gain (9.25 hp)
Peak 9% gain (16.65 hp)
Max 14% gain (25.9 hp)
Peak 15% gain (27.75 hp)
Max 23% gain (42.55 hp)
Cobb numbers are all after drivetrain loss, it looks like this tune matches up pretty closely to a stage 2 Cobb tune if you were to factor in drivetrain loss.
I don't doubt that the tune can pull it off,I don't know what strategy they are using to achieve the results, though. I could run a stage 2 cobb OTS tune without the intercooler and it would work but it would probably be less reliable and more risky for the engine given the higher charge air temps. It would be fine for about 1 - 2 pulls, or non-aggressive driving, though.