I just found this bug on my fresh installation 4.7.1. Tested on flynax demo, same issue.
If you only have 1 available plan for any category. You can't limit time usage. Basically, user can post as many times as they like, using the plan that admin set 1 time usage only. ((
Here is how I tested on DEMO,
First I set time usage of free package to one, and leave other packages active. Try to post new ads, it says I used up free package and asked to try other plan. OK
Then I tried to set all other packages inactive, only leave free package (set 1 time usage) active. And that they can post as many times as they want. not OK
Would you please fix this.