In the numerator of VTE3 there are several sections of logic similar to this:

■AND: Difference between dates >= 4 day(s) of:
■AND: FIRST:
■OR: "Medication, Administered: Parenteral Anticoagulant" < 1 day(s) starts after start of ("Medication, Administered: Warfarin" during "Occurrence A of Encounter, Performed: Emergency Department Visit")
■OR: "Medication, Administered: Parenteral Anticoagulant" < 1 day(s) starts after start of ("Medication, Administered: Warfarin" during "Occurrence A of Encounter, Performed: Inpatient Encounter")
■OR: "Medication, Administered: Warfarin" < 1 day(s) starts after start of ("Medication, Administered: Parenteral Anticoagulant" during "Occurrence A of Encounter, Performed: Emergency Department Visit")
■OR: "Medication, Administered: Warfarin" < 1 day(s) starts after start of ("Medication, Administered: Parenteral Anticoagulant" during "Occurrence A of Encounter, Performed: Inpatient Encounter")
■AND: MOST RECENT:
■OR: "Medication, Administered: Parenteral Anticoagulant" during "Occurrence A of Encounter, Performed: Emergency Department Visit"
■OR: "Medication, Administered: Parenteral Anticoagulant" during "Occurrence A of Encounter, Performed: Inpatient Encounter"

Each Medication, Administered has a Start DateTime and an End DateTime

Scenario:
First qualifying Medication Administered occured with a start datetime of 10/1/13 23:50 and an end datetime of 10/2/13 00:20
Most Recent qualifying Medication Administered occured with a start datetime of 10/4/13 23:50 and an End DateTime of 10/5/13 00:20

Which dates are you comparing to make the calculation "Difference between dates >= 4 day(s) of"

Is it comparing:
1) start datetime of First to start datetime of Most Recent (3 days in scenario above)
2) start datetime of First to end datetime of Most Recent (4 days in scenario above)
3) end datetime of First to start datetime of Most Recent (2 days in scenario above)
4) end datetime of First to end datetime of Most Recent (3 days in scenario above)