13 skills slottable?

Hello, under 'Input' and in the UI I can see up to 13 skills slottable - including those with the ctrl-modifier.

Yet, in the skill assignment menu - from which skills can be dragged to slot - 11 is the maximum number of skills I can have active. I'm level 18. Is that number to increase up to 13 via level-up later?

Thanks for reply.

anyone know what's up regarding this!?

Can someone verify this answer I came up with:

So the maximum of 13 skill-keybinds is for people who use 2 unset rings.

As with this type of ring they can slot 1 more skill for each ring respectively.

Is that correct?