mailgraph count sent item last week more than last day

[dedeon]

Excuse me, I'm using mailgraph 1.14 on ubuntu 10.04 with postfix 2.7, amavisd-new, clamav and spamassassin. My problem is whether the number of emails sent and received on the graph last week more than the chart of last day? I mean my sent item at last day graph is 50, but on last week is 55. I just run postfix for 3 hours, but why mailgraph display like that, whether mailgraph count like that? I've enable ignore-localhost = true. thanks for your help