My guess is that it's a (L)ock-out vs. a (D)edicated. A lock-out Studio has an internal door that connects it to a 1 BR lockout which together can form a 2 BR. A Dedicated Studio has no such door....
I would guess, though that it is Studio Lock-off and Studio Dedicated.
Lock-off studios have a connecting door to a one bedroom unit so they can be converted into a 2 bedroom unit. Dedicated Studios are not connected toa 1 bedroom, some (at BWV) have a bench or very small daybed and used to be referred to as a "studio plus"
Not all DVC resorts have dedicated studios, and AFAIK, only BWV dedicated studios have the bench/daybed.