Paladin Aura of Protection

The tool-tip and ability description both say that the aura give a +4 bonus to saving throws. But the observed behavior is that the paladin gets a +3 and the party members only get +2. By looking at the ability modifiers and proficiency bonus of the paladin you can see that the increase is just +3. And for other party members just move them in or out of the area and see that they only get +2 when in the area of effect.