Why some messages could be edited by the authors, but some not

There is a thing that is happening in my forum and I don´t understand why. In some messages written by a member appears the possibility of editing the post and in anothers not. I do know that a member cannot edit other member´s ones but his own ones yes.

Somebody knows why happens this?

RTFM:

http://www.minibb.com/forums/manual.html#config2

$useredit=86400; Parameter defines number of seconds, after which user WILL NOT BE ABLE to edit his message. By default is 1 day (86400 sec.) If 0 or not set, user will be able to edit his post everytime.

Ok, thank you a lot. You are really really efficient.