FIeld Icons and Behavior

I've used just about every BI tool on the market, but am new to Power BI. 

What I would expect is that I can apply my filters in the formula, use the column, and specify the aggregation level to sum on the panel (or in the model, but not in the formula).  But hee's what I get:

I have 2 formulas (calculated fields) that are virtually identical.  The only difference is the OrderType filter and they are opposite filters and should almost add up to the SUM amount (except for the DSN filter).  I would think they would behave the same but they are displaying different icons and behaving differently.  Both use the same single datasource which is a SQL Server query.

SUM = SUMX(FILTER('Previous Year Bookings','Previous Year Bookings'[PY Month]=MONTH(today())),'Previous Year Bookings'[PY Amount])

         SUM displays a little column icon with a Sigma overlayed and allows all of the aggregate options.

A = SUMX(FILTER('Previous Year Bookings','Previous Year Bookings'[PY Month]=MONTH(today())&&'Previous Year Bookings'[PY Prefix]<>"DSN"&&'Previous Year Bookings'[OrderType]="Non-Capital"),'Previous Year Bookings'[PY Amount]) 

         A displays the calculator icon and only allows 'No Calculation' or 'Pct of Total' options

B = SUMX(FILTER('Previous Year Bookings','Previous Year Bookings'[PY Month]=MONTH(today())&&'Previous Year Bookings'[PY Prefix]<>"DSN"&&'Previous Year Bookings'[OrderType]="Capital"),'Previous Year Bookings'[PY Amount])

         B displays a little column icon with a Sigma overlayed and allows all of the aggregate options. I also seem unable to control decimal display when this is the icon.

What am I missing?