How does `ekaf_max_buffer_size` work?

I changed this parameter to `2`, but after 2 messages emitted I don't see messages in kafka topic.
However `ekaf_buffer_ttl` does work: when I change ttl from 2 seconds to 10 seconds I see the difference when messages are flushed. I checked using `application:get_env` that both parameters are set.

Thanks.