When the Lookup data is edited on the Account Details/Assumption screen, the Refresh Lookup Syn Status functionality can be used to confirm that the data has been changed.  When the data has been changed the box turns from "Green" to "Red" as per the below.

To find out the exact change that occurred:

1) Click on the "Lookup Sync Status" tab; then

2) Click on the red box to activate the data display (this can take a few moments as there is a lot of data to search).

Then the Variance between the Lookup Source and Actual Account will display. In this example as highlighted, an additional $50 was added in Jun.