Need help interpreting panel specification
What they mean by this is known as a stab rating

What they mean by "connector" here is the tabs, or "stabs", that stick out from the busbars and make contact with jaws on the breakers.  In other words, each bus stab on your panel can handle a maximum of 125A of load, which can be split however you'd wish across the breaker poles on each side of the stab.

For instance, if you had a 100A 2-pole breaker mounted in the two bottom left spaces, you are limited to 25A on each of the two poles across from it (in the bottom right spaces, in other words), which practically limits you to 15A and 20A circuits as there just isn't that much that runs on a 25A breaker.