Imported Data Not Stored Correctly in dataViews[0]

I have a custom visual that reads in data from three columns in Excel into a table.  My test columns look like this:

  A  |  B  |   C

-------------------

  0  |     | Name0

  1  |  0  | Name1

  2  |  1  | Name2

  3  |  2  | Name3

  4  |  3  | Name4

  5  |  4  | Name5

In the dataRoles section of capabilities.json, the kind for the three data fields is declared as "GroupingOrMeasure". 

When I inspect dataViews[0].table.rows in the developer panel of my browser, all data values for column A are 1's.  One row of column B contains a 'null', which is correct.  However, the rest of the rows contain 1's.  All strings for column C are correct. 

This is how the data looks in dataViews[0].table:

  A  |  B   |   C

--------------------

  1  | null | Name0

  1  |   1  | Name1

  1  |   1  | Name2

  1  |   1  | Name3

  1  |   1  | Name4

  1  |   1  | Name5

I am on API 1.8.0 and don't recall running into this problem with earlier API's.

Any ideas?  Thanks.