Hi Matthias,
the parameter "OPERATOR" is a relique from an old Automic version. Here a screenshot of the good old times of Version 5.00A
https://us.v-cdn.net/5019921/uploads/editor/z8/hgaiybxk1c3z.png" width="959">
I dont know when it was changed, but it came from the time when the Notification Object was called "CallOperator" which was changed from Version 8.00A to 9.00A, if i dont speak the truth, Banhammer should speak over me ;)
The Parameter PUT_ATT Operator is still working, but it should not be used in new created objects (and if you have the chance to change it in older objects, I would suggest to do it)
** EDIT: Sorry for the german screenshot, i only had a german Version of 5.00A documentation available on my hand, but you get the gist.