Sort users issue in Members Directory

Hi there,

I got an issue with the sorting of the Members Directory.
I’ve added a ‘number’ meta in people’s profile (in this case house nr), and have sorted by number which should be from 1 to 100. It kinda does but not correct.
It first shows 1, than 11, 12 etc and after 19 comes 2. As 2 doesn’t start with a 1 it comes later than 11 or 12, but it should come obviously in normal order of 1,2,3,4,5..10,11,12..20 etc.

I hope this is clear although many numbers here. I’ve tried various meta’s like numbers, a custom one and a dropdown, but none will work and all showed the same. Even tried 02 instead of 2.

Can someone help me and explain what to do with the settings / meta?

Thanks
Pepijn

The page I need help with: [log in to see the link]