Log4j2.properties

Can someone please explain theses two things in the Log4j.2 properties file in ElasticSearch

`appender.index_search_slowlog_rolling.policies.time.type=TimeBasedTriggeringPolicy
 appender.index_search_slowlog_rolling.policies.time.interval = 1`

I want to understand how the slow log file will get deleted, as I have memory limitations.
And I am unable to make it a time based policy - getting the below error

curl --location --request PUT 'localhost:9200/_settings?pretty' \ --header 'Content-Type: application/json' \ --data-raw '{ "appender.rolling.policies.size.type" : "SizeBasedTriggeringPolicy", "appender.rolling.policies.size.size" : "256MB" }'

{ "error": { "root_cause": [ { "type": "illegal_argument_exception", "reason": "unknown setting [index.appender.rolling.policies.size.size] please check that any required plugins are installed, or check the breaking changes documentation for removed settings" } ], "type": "illegal_argument_exception", "reason": "unknown setting [index.appender.rolling.policies.size.size] please check that any required plugins are installed, or check the breaking changes documentation for removed settings", "suppressed": [ { "type": "illegal_argument_exception", "reason": "unknown setting [index.appender.rolling.policies.size.type] please check that any required plugins are installed, or check the breaking changes documentation for removed settings" } ] }, "status": 400 }