If you want distinct patients, you should probably be grouping based on something relative to the patient - name, MRN, combination of two (my preference). That should solve the issue of only one entry per person.
You might also want to create a field called something like LastTime defined as:
if {LASTLABS.HDID} in [172763.00, 172764.00]
  then {LASTLABS.MAXLABDATE}

and then at the Group Level for the person, do a summary (weird E on icons) to show the maximum value for LastTime

You probably want to also do a summary on the person field (name or MRN or combination) for a distinct count at grand total level