So...OP was leaving this morning. Unless he left quite early, the answers he got here, would still leave him wondering. I will guess he left them at pressure tire shop used, when they installed. If he would have used the same rated tire, as per his trailer placard, 65 psi is indicated as needed inflation for his trailer.
What CapriRacer posted makes sense to many of us, but may have confused the OP even more??
At least he is leaving with new, quality tires. There is good info out there for him to research, concerning ST trailer tires. A former member here, Roger Marble has a dedicated RV tire blog that he could gain knowledge from.
Jerry