Frontend's trigger expression condition editor says that:
"fuzzytime() - Difference between item timestamp value and Zabbix server timestamp is over T seconds (1 - true, 0 - false)"

however, I believe the correct fuzzytime return values would be (0 - true, 1 - false), as stated in the manual:
https://www.zabbix.com/documentation/4.0/manual/appendix/triggers/functions