User blog comment:Ash9876/Welcome to the Ultimate Magic World/@comment-24039725-20160930144506/@comment-5914413-20160930171502

Not yet, we had 5 guild masters in a normal sequence, then during the time skip there was a 6th one that gave the seat back to the 5th, then gildarts was made the 7th guild master who gave it back after allowing laxus back in the guild. After the avatar arc Erza was the 8th guild master (think hers was more of a temporary one instead of supposed to be permanent ) and she gave it back to the 5th again.

All in all, that rounds up to 11 changes if i remember every change and Ash here is the 4th one i guess?