You can remove obsolete acknowledgements using the Clear push-button.
To clear obsolete acknowledgements:
Follow the procedure Checking for vehicle order acknowledgements.
The form's grid lists unprocessed acknowledgement records (indicated by the Unprocessed radio button being selected).
Tip: To clear acknowledgement records from the on-hold or exceptions lists, select the On-hold or Exceptions radio button or select View > On-hold or View > Exceptions from the menu bar, respectively.
Tick the lines to be included in the clearing action and click the Clear push-button.
Note:
All acknowledgements whose check grid column is ticked are included in the clearing action. Records can be toggled in/out by either a left-double-click or by selecting the Select acknowledgement option from the line's right-click menu. Similarly, the entire list can be included or excluded by selecting Edit > Select all 
or Edit > Deselect all 
from the menu bar or toolbar, respectively.
The Progress bar indicates how much of the process has been completed as an approximate proportion of the whole. On completion, an Information dialog displays the following message:
INFO: All selected records were successfully cleared