The default start time (or be there by time) is based off the "match time" entered on the "create schedule" (or edit schedule) page.
You can also change the match times line by line though in the "create lineup" page.
If you have lots of matches that have "split times" like this you may want to enable the "early / late" options for the availability page -- by default it is "off" but you can turn it one easily from the "set/view availability" page (link found on the "matches & teams" page).