The update seems to be working correctly with the sample data. The results don't match but that's only because you're adding the order number to the description.

Here are my suggestions depending on the data type.
DECLARE @NUMLIST TABLE
(
NM_ID INT IDENTITY(1,1) NOT NULL PRIMARY KEY CLUSTERED
,SKU BIGINT  NOT NULL
);

This should be the equivalent to the original query using EXISTS instead of IN.
SELECT
  ap.AdminProduct_ID
  ,ap.RowVersionNumber
  ,ap.TherapyAdmin_ID
  ,ap.PackagedProduct_ID
  ,ap.AdminRecordMethod
  ,ap.ActionCode