why do i receive multiple Events for same operation with pull subscription

I have a pull subscription to two resources in exchange

For almost any operation there are always multiple events (they appear to be duplicates)

for example:

i have 2 resource mailboxes in a calendar appointment, my pull subscription gathers the creation events and im up to date

then i move the appointment to the next hour

I receive 4 (should be 2 imo) ItemEvents!

gathered appointment og test 8 for NH-SX80@nh.vnoc2.com 
itemId AAMkADhkM2RjZDlkLWY1NWEtNGQ5YS1hOGMwLTFlNzhkYjA0MzljNwBGAAAAAABzcFw7M0ZjQ5vOUNrMTWNRBwB7Pwt5oBwUTLLxFipuBzo3AAAAAAENAAB7Pwt5oBwUTLLxFipuBzo3AAN7T/S1AAA= 
icalid 040000008200E00074C5B7101A82E00800000000251D5DB367EED50100000000000000001000000062B8FD572D584D4BBA6AAD6DA71ACE2B
itemEvent type of: Modified.

gathered appointment og test 8 for NH-SX80@nh.vnoc2.com
itemId AAMkADhkM2RjZDlkLWY1NWEtNGQ5YS1hOGMwLTFlNzhkYjA0MzljNwBGAAAAAABzcFw7M0ZjQ5vOUNrMTWNRBwB7Pwt5oBwUTLLxFipuBzo3AAAAAAENAAB7Pwt5oBwUTLLxFipuBzo3AAN7T/S1AAA= 
icalid 040000008200E00074C5B7101A82E00800000000251D5DB367EED50100000000000000001000000062B8FD572D584D4BBA6AAD6DA71ACE2B
itemEvent type of: Modified.

gathered appointment og test 8 for NH-DX80@nh.vnoc2.com
itemId AAMkADY3NDRjMzIwLWVkZDEtNGJlZS04N2RmLTE5MjlmZWYzOTY3ZABGAAAAAAAkKeFNMPOwRYhpC8onqAS7BwB+I8Xon2TYQ54o8FGxtwxFAAAAAAENAAB+I8Xon2TYQ54o8FGxtwxFAANN4melAAA= 
icalid 040000008200E00074C5B7101A82E00800000000251D5DB367EED50100000000000000001000000062B8FD572D584D4BBA6AAD6DA71ACE2B
itemEvent type of: Modified.

gathered appointment og test 8 for NH-DX80@nh.vnoc2.com
itemId AAMkADY3NDRjMzIwLWVkZDEtNGJlZS04N2RmLTE5MjlmZWYzOTY3ZABGAAAAAAAkKeFNMPOwRYhpC8onqAS7BwB+I8Xon2TYQ54o8FGxtwxFAAAAAAENAAB+I8Xon2TYQ54o8FGxtwxFAANN4melAAA= 
icalid 040000008200E00074C5B7101A82E00800000000251D5DB367EED50100000000000000001000000062B8FD572D584D4BBA6AAD6DA71ACE2B
itemEvent type of: Modified.

we can see from the above that the itemid changed but not the appointment (icalid)

So my question is why are there so many events for a single operation?  This was a single operation (move the appointment) i would expect 2 itemevents, 1 for each resources mailbox that was effected