In all likelyhood, the adept power is meant to be able to add "+50%", so maximum 3 rating at the beginning (or 4 if you get Aptitude and bring the skill to 7 ranks). It fits with the theme that adepts use magic to enhance their own existing abilities and attributes, rather than relying entirely on magic or using it as a crutch to replace genuine skill. If the adept could have more levels of Improved Ability than they did points in the skill, that wouldn't fit. More importantly though, it would be terribly unbalanced if an adept could start the game with such a significant boost to a skill, even if it would cost most of their PP.
Even if you were able to take 1.5x your skill in levels of the power, all adept powers have a cap of (MAG), so you couldn't get more than 6.
If you think it's something that is genuinely too unclear, then I'll mention it to the rest of the errata team.