Different voters have different effects on the voting threshold.
It's sort of broken as is much of the stuff around garage.
I believe it should be 10 "normal" votes or 6 votes if a dev or special garage member has voted. Now that most packages are realised by a small cluster of people and instantly voted up by the maintainer packages generally have a 6 threshold.

I have managed to enable promotion on many of the packages stuck in testing due to this.