https://www.zabbix.com/documentation/2.2/manual/config/items/itemtypes/aggregate
https://www.zabbix.com/documentation/2.4/manual/config/items/itemtypes/aggregate

it shows using "0" as a parameter for function last() - that should not be required since 2.2.0 as per ZBX-6883

also, note "The timeperiod parameter is ignored by the server if the third parameter (item function) is last." should be reviewed - is that still the case ?