Trigger function .min() not working

[oldfox]

Hi
I got problem with trigger function.
I create such trigger:

{Service_MsSQLerf_counter["\MSSQL${$SQL1}:Buffer Manager\Page Life Expectancy"].min(1800)}<{$MSSQL_PAGE_LIFE}

Which mean trigger should activate after 30 min if all values are below {$MSSQL_PAGE_LIFE} macro value

Problem is that even one last value is below {$MSSQL_PAGE_LIFE}=300 activate the trigger

2015-06-12 13:14:54 247
2015-06-12 13:09:54 879
2015-06-12 13:04:59 714
2015-06-12 12:59:54 442
2015-06-12 12:54:54 442

What is funny. Trigger come back to OK state after .. 30 min

I try with min(30m) and min(#6)

Zabbix 2.4.2

Thank you for help

Regards
Pawel

OK
I found
I should use function max instead of min