Accordingly to Documentation: https://www.zabbix.com/documentation/current/manual/appendix/functions/history

count() function's second parameter (time period) is mandatory. In frontend it is not possible to create such item or trigger without given time period in count function:

But if such function is passed to Zabbix server, for example in macro in action messages or media type templates: {?count(//trap)}, then such macro is resolved and function result is always 1.

Need to understand which behavior is correct and unify server, frontend and documentation.