The maximum power of the characters does not rise above 129 percent (The Witcher 3: Wild Hunt)

Collected a complete set of Gryphon armor workshop and noted that more 129 proektov to the power of symbols is not added (according to the statistics in the game). At the same time, which is strange swords do not add strength to the signs, even though their characteristics are specified +20 percent. Mutagens give approximately +30 percent (10 for each skill branch characters). At all so or is it a bug?