Why is the PMPM amount different in two Quick Reports run on the same day?

Problem

Can you help me understand why the PMPM amount would be different in these two Quick Reports run on the same day: Historical & Goal Benchmark - Summary by TIN & NPI vs PMPM Claims Summary - Summary by TIN & NPI?

Solution

Historical Goal Benchmark = Part A + Part B + Part B DME Spend for Attributed Patients / # of patients we have Spend Numbers for / # of Months that we have claims for.

PMPM Claim Summary = Part A + Part B + Part B DME spend for attributed patients / Member Months (we check for each patient how many member months they actual had in the reporting period)