If your timecode display is looks like this 0;00;00;00 then your frame rate can't be 30 fps. It's probably 29.97 fps.
If your composition is 300 frames long then at 29.97 fps the Drop Frame Timecode display would be 0:00:09:29 when the time line indicator is at the end of the composition. The timecode displays the hours, minutes, seconds and frames corrected to correspond to real time. Because you're counting in base 30 (thirty frames per second) but the footage is actually running a little slower (29.97 frames per second) the timecode display skips some frame numbers so that the hours, minutes, and seconds part of the display corresponds to real time.
The reason that the timecode display doesn't read 0;00;10;00 is that the CTI (current time indicator) is parked at the head of the last frame and showing you the last frame, and telling you at what time the last frame is going to start playing.
If your frame rate is the standard NTSC 29.97 and your timecode display is set to NON Drop Frame you should see 0:00:09:29 as the display because that's how the numbers work out. However if your composition was 10 minutes long you'd have 17982 frames (29.97 X 60 X 10) your Drop Frame timecode display would be 0;09;59;29 but your Non Drop Frame timecode display would be 0:09:59:11. As you can see, the hours, minutes and seconds are still close, but the frames are off by about two thirds of a second. You still have the same number of frames, but the time display is off. Drop Frame timecode display was created so that you could easily determine the actual playing time of a video tape. If you were dealing with hour long programs your programs would be about 5 seconds short.
I hope this didn't confuse you.
If your project is actually 30 frames per second then there drop frame timecode could not be applied to your project.