A lot of people seem too focused on the max, peak. or hp bragging rights, the tune I had on the Golf R basically added 33 hp (plus or minus a few hp) right across the rpm range from 3000rpm upwards, the increase in the mid range was far more useful and noticeable than the increase at the top end
The additional 33 hp at 6800rpm would be around a 10% increase.
The additional 33 hp at 3500rpm would be around a 16.5% increase
PS: The added 33hp was on actual values, they tested the Golf R at 328hp, so 328+33hp as the final figure, some companies would use the VW 306hp figure and compare their new figure to that making the 33hp increase a 55hp increase