I don't mind spending some time thinking about this with you.
So the way people will see what you post is if they use the same relays you're using. They might get a post of two through the grapevine of users sharing with each other but direct access to the relays you're using will be the best way for them to get you posts. That being said, if you're using 13 relays that mean your are posting your content on all 13 of those relays and chances are good that is enough to propagate your posts through nostr making it available for users to see it.
Now there is also relays that you can install and setup that have features that will allow you to spread your posts and content to other relays, this way you can use one relay and have it distribute your content to other relays on the network.
Strfry is one of these relays.