Alternator overcharging

From the numbers you posted the charging system is working the way it should. That system charges from battery voltage up to 15.5 or so normally. Try this test, measure the battery voltage with everything off. Now start the truck and turn on the headlights, A/C on max, blower motor on high and heated seats on if it has them. Now measure the voltage at the battery. Is it above 13 volts up to 15.5? Yes, system is charging okay.

Sounds like it's doing fine. The modern systems are fun to test because of the way they are controlled. Some of them charge in steps where they hit 15+ volts to bring the battery up to full charge rapidly right after you start the vehicle, then drop down to a steady rate then some even stop charging entirely until there is a load placed on the system like lights or heat. Yours is more the first one with multiple charge steps to keep the battery charged. If you had seen 15 or higher with everything on then you would be concerned, and the first thing to do would be to clean the battery terminals and check the grounds on the engine to chassis cables as those having corrosion is common and the system will raise the charging voltage up to compensate for that.