When creating a KPI visual, it appears that if you perform the steps in a different order, you get different results. Consider the screen shot below. The KPI on the left was created by first selecting the KPI visual from the pallette, then dragging NET SALES to the Indicator and PERIOD_START_DATE to the Trend axis. To verify that it is displaying correctly, there is a line chart below it that pretty much shows the exact same data shape. And the last data point on the line is the $523,402 as reported on the KPI.
THe KPI on the right, however, was created by the following steps:
Select NET SALES (which created a new Clustered Column Chart to be added to the canvas).
Highlight the visual and make it a KPI
Add PERIOD_START_DATE to the Trend Axis.
In the end, BOTH KPI visuals have NET SALES as the Indicator and PERIOD_START_DATE as the Trend Axis, and nothing in the Target goals, yet the visual shape and number reported are different.
What's more, if you REMOVE NET SALES from the one on the right, then add it back, you get the correct visual.