"1% huh, getting 1% improvement just from the 1st training, that’s not bad." After all, all the secret techniques he picked out of his expert memory were not just any random simple secret technique. If they weren’t one discovered by the ancients, it would be a high-leveled secret technique developed by the major gates in the world of Wushu.
Not only that, all of the selected secret techniques had a common trait; they are all secret techniques that Garen could not "see through". At his level of expertise, an average secret technique could be effortlessly mimicked by him, even without training. Only secret techniques that were at an extremely high level or self-pioneered in a field that Garen had no experience in could not be "seen through" by him.