Ok so all rods have a certain # test they can handle but when a rod says 10-20 # test for example but you will be using braided line how do you know what you can and can't use? Sorry if this question is confusing.

Your question is not confusing.  The numbers are suggestions.  It’s not about the line size as much as it is about the weight of the bait you will be using.  For my bait casters I use 50 no matter what it says on the rod.

I think those specs started as indications of the max dead lift capacity of the blank, but I don't know for sure.  I don't use them for anything.

 

The specs that are meaningful,but somewhat subjective, are the power (heavy, medium heavy, medium, etc.), action (fast, Xfast, moderate, etc.), and the lure weight suggestion.  They can guide you to a rod that fairly well meets your technique requirements, especially when you've used a lot of rods and learned how to correlate the specs with your preferences.  

 

Use any line type and pound test you find works for you and use your drag and how you point the rod to manage the stress on the rod.  You do not want to take the modern high modulus rods beyond  90 degrees deflection.  Some will take it, some will not.  But the higher the modulus the more sensitive to mis-handling they are.