[exim] Maximum number of SMTP connections

Hi,

I have not set smtp_accept_max in my Exim configuration. The manual
states that there is a default value of 20.

I recorded

netstat -t | grep -E "^[^:]+:smtp" | wc -l

for some time now, to see how the number of SMTP connections evolves
over time. The maximum was 39. Why?

Thanks,
Peter