I know the Pairwise Rank isn’t only dependent on RPI, there are other factors involved, which they must split in those comparisons...hence the tie.
I apologize if I'm restating things said by others but I wanted to try my hand at explaining it as I understand it:
PWR is done by comparing every team against each other and each time they beat a team they get a point. Then they rank the teams by most points to lowest. To understand where a team is in PWR one should arrive at how they won or lost the comparison to all the other teams.
Three criteria are used to compare each team to each other: win percentage against common opponents, head-to-head record and RPI. Most points are based on RPI alone because there were only 12 inter-region games in DIII this season, leaving a lot of 0-0 ties in both the winning % against common opponent and H2H criteria.
Let's look at the top and bottom of the PWR:
Plattsburgh currently has the maximum 66 points which means they beat every team when comparing criteria. Their RPI is the highest in the league so the only way someone can pick up a point on them is to have both of the other two criteria over them. No one can claim an outright win against them in head-to-head right now as they avenged their one loss to Midd. Also, no one can claim a better winning % against common opponents because the only other team to beat Midd is Hamilton and they also are 1-1 vs Midd.
Alvernia has 0 points because they are last in RPI. This gives every team that has beaten them or hasn't played them an automatic point. The only team they go to a third criteria with is Anna Maria, and Anna Maria wins the comparison by having a better winning % against common opponents because they beat and tied King's whereas Alvernia lost to them 3 times.
To understand why there are ties in PWR one would have to lay out the criteria to see who picks up points against who to see how they arrived at the same number of comparisons.
With Endicott and GAC tied at 62 points it means they don't pick up points against 4 teams.
For Endicott, they beat everyone in RPI except Plattsburgh, Eau Claire and Midd. Middlebury gets the point when the two compare because they beat them H2H on 1/11. Plattsburgh and Endicott haven't played so they tie H2H. Where the Cardinals pick up a point on them is that they are 4-1 against common opponents compared to Endicott's 0-2. Eau Claire gets their point on RPI alone because they and Endicott haven't played and have no common opponents. Other than the three teams ahead of them in RPI, the only team Endicott loses a point to is Norwich. Norwich's H2H and winning percentage against common opponents Southern Maine and Middlebury overcome Endicott's RPI advantage.
For GAC they miss 4 points because they lose the one to one comparisons to the teams above and tied with them. Middlebury and Endicott get points on RPI alone because they have no other category to compare with GAC. Plattsburgh and Eau Claire beats the Gusties in both RPI and winning percentage against common opponents.