[exim] How to interpret pasted snip of log?

Hi!
I'm looking at
http://www.exim.org/exim-html-current/doc/html/spec_html/ch-log_files.html
and I can't find answer. I'm wondering why I've got in main_log
H=(mnch-4d044ae7.pool.mediaWays.net) in first line, and
H=mnch-4d044ae7.pool.mediaways.net in second line in the same delivery?

Second line is more correct for me because 77.4.74.231 has FCRDNS.
Below is snippet from log:
2013-01-03 16:24:55 1Tqmf8-0001lO-JU
H=(mnch-4d044ae7.pool.mediaWays.net) [77.4.74.231] I=[77.252.119.98]:25
Warning: Punkty SA:255
2013-01-03 16:24:55 1Tqmf8-0001lO-JU H=mnch-4d044ae7.pool.mediaways.net
[77.4.74.231] I=[77.252.119.98]:25 Warning: to jest spam

And here is snippet frm exim.conf:
acl_smtp_data = acl_check_data
[...]
acl_check_data:
[...]
warn
                message         = X-Spam-Score:$spam_score_int
                spam            = nobody:true
                log_message     = Punkty SA:$spam_score_int
[...]
warn
                message         = This message scored $spam_score spam
points. / Ta wiadomosc to spam.
                # set acl_m1    = ham
                spam            = nobody:true
                condition       = ${if >{$spam_score_int}{55}{1}{0}}
                set acl_m1      = spam
                control         = fakereject/Rejected.This message
scored $spam_score spam points.SC. / Ta wiadomosc to spam. Zostala
odrzucona.
                log_message     = to jest spam
                #delay          = 1s

Could it be result of delaying in dns resolving?
Marcin