What is the difference in my two equations? Array.

[TexasBobcat]

I have two formulas.

1. =SUM(SUMIFS(PSR420T[ADV],PSR420T[BLK],[@Block],PSR420T[BusType],"<>C",PSR420T[BusType],"<>P"))

2. =SUM(SUMIFS(PSR420T[ADV],PSR420T[BLK],[@Block],PSR420T[BusType],{"C","P"}))

What is the difference in the ending of my formulas?

[Ron Coderre]

Formula 1 is all inclusive and does not need the SUM function wrapper.
It resolves to:
Sum [ADV] Where [BLK]=Block and [BusType]<>C and [BusType]<>P

The second uses a fixed array and does require the SUM function wrapper.
It resolves to
SUM(
Sum [ADV] Where [BLK]=Block and [BusType]=C
Sum [ADV] Where [BLK]=Block and [BusType]=P
)

Does that help?