Based on RecordType, this field indicates the operation performed by the record. For this log type its value is 4. For available RecordType values, you can visit Microsoft’s documentation here.
CUSTOMEVENT
Based on CustomEvent, this field contains the optional string value for custom events.
EVENTDATA
Based on EventData, this field contains the optional payload for custom events.
MODIFIEDPROPERTIES
Based on ModifiedProperties, a structure field that contains details such as: modified property, current value of the modified property and the new value of the modified property.
SNAREDATAMAP
All unclassified field(s) parsed from this log type will be pushed into the SNAREDATAMAP.
Note: See other fields here, which are common among all SharePoint* log types.