booktype to dvd-rom supposed to be greyed out

i have dvd shrink and i was wanting to make sure that i was burning to dvd-rom booktype , i have a new lite on lh 20a1p burner and it supports booktype or bitsetting as it is called , when i go to backup the option for booktype to dvd -rom is checked but greyed out were you cannot change it . is this a default setting , or does this mean that it is set to dvd-rom and it can not be changed . thanks