Sum Aggregation From the Month Level Overwrites Quarters. All 12 months, four quarters, and the year are in status. Jan, Feb, and Mar each have a value of 2, which adds up to 6. The 6 overwrites the previous value of 9 in Q1. Apr is NA, and May and Jun each have a value of 2, adding up to 4. The 4 overwrites the previous value of 5 in Q2. Jul has a value of 2, and Aug and Sep are NA, adding up to 2. The 2 overwrites the previous value of 3 in Q3. Oct and Dec have a value of 2, and Nov is NA, adding up to 4. The 4 overwrites the previous value of 7 in Q4. The four quarters add up to 16 for the year.