Following description in the manual is incorrect.

https://www.zabbix.com/documentation/4.0/en/manual/config/items/itemtypes/log_items#using-maxdelay-parameter

https://www.zabbix.com/documentation/5.0/en/manual/config/items/itemtypes/log_items#using-maxdelay-parameter

https://www.zabbix.com/documentation/6.0/en/manual/config/items/itemtypes/log_items#using-maxdelay-parameter

https://www.zabbix.com/documentation/6.2/en/manual/config/items/itemtypes/log_items#using-maxdelay-parameter

Built-in protection against overload consists of a configurable 'maxlines' parameter (protects server from too many incoming matching log lines) and a 4'maxlines'* limit (protects host CPU and I/O from overloading by agent in one check). 

4*'maxlines' is incorrect.

10*'maxlines' is the correct formula.

For reference, In The "Important notes" section describes it as "10 times".

To find the required string Zabbix will process 10 times more new lines than set in MaxLinesPerSecond. Thus, for example, if a log[] or logrt[] item has Update interval of 1 second, by default the agent will analyze no more than 200 log file records and will send no more than 20 matching records to Zabbix server in one check.