[Publish] What does "number of scheduled posts" mean?

Depending on your plan, you'll be able to schedule a certain number of posts in advance.

This is not a weekly or monthly limit, it's the number of posts you can store in your queue at any one time. Let’s say you are on the Pro Plan and already have 100 posts in your queue. You will not have the option to add any more posts. However, as soon as one of your posts gets published, you’ll be able to jump in and top your queue back up to 100. If you share 10 posts per day, you would be able to schedule 10 days in advance on the Pro Plan.