@Hollow7F
No, they are not limited. @Owyn
Numbering skills mean that they are unique only one person could hold such a skill at a time and they are really powerful.
They explained it in the beginning of the story when he got the skill from the Batory vampire dagger at the ant cave in the tutorial.
@Owyn It was explained in the beginning. In simplest, super strong skills or created skills are registered in the tower with the numbering system. The smaller the number, the stronger the skill. He got the vampire skill in the beginning that let him suck stats and skills.