[exim] QT=... DT=... vs timestamp

Hello,

the QT= computation must be broken :-(

2016-10-04 04:29:46 1brF1V-0005H0-Gs <= redacted@??? U=root P=local S=600232 T="Cron <root@redacted> /usr/local/sbin/Mirror" from <root@???> for root
2016-10-04 04:29:56 1brF1V-0005H0-Gs => redacted@??? F=<redacted@???> R=remote T=smtp S=608364 H=mail.shuttle.de [194.95.249.4] X=TLSv1:DHE-RSA-AES256-SHA:256 A=client C="250 2.0.0 Ok: queued as 20F1AC1" QT=29m55s DT=10s
2016-10-04 04:29:56 1brF1V-0005H0-Gs Completed QT=29m55s


The DT= is correct, but what about the QT= ???

Exim version 4.85 #8 built 18-Feb-2016 14:56:42



Confused, Frank Elsner