When booking directly with DL, they provide fare construction/component and pricing breakdown in Fare Details: line of the email receipt which can be helpful. Did you book directly with DL on original itin or through TA? I'm assuming these were all DL coded flights and the Delta website shows Reward Method 'R' (which means credit was based on fare price and not distance) on activity page? Did TA apply credit from cancelled flights to new flights back or were these with a different carrier?