Channel join power question

Hi,

I am a member of the Super Admin group.
I removed b_client_skip_channelgroup_permissions to try and work out the permissions.

I made a channel, set the join to 75.
But admins with join power of 75 (+ grant 75) cannot get into the channel.
If I set the channel join permission to 50.. I can get in. Why is this?

thanks

Channel join power question