Formatting Problems with mini-dvd?

when i first purchased my vdrm53, discs formats were still 30 min to shoot .. now, after initial formatting of new disc, the display says that i have 19 minutes of shooting time .. what settings could i have changed in my camcorder? please help?

have u tried adjusting the long play and standard play settings in the camcorder(lp/sp) these generally increase or decrease the play time of a disc by degrading qual