Standard NTFS rate is 30 frames per second, or 1 frame for every 33 msecs. You can zoom in on the timeline to 1 frame increments, insert your text overlay (probably track2 or higher), and then specify the length of time you want it to appear. You'll have to do this for each location you want your text to appear. You'll also have to experiment with the duration of the text overlay to get the effect you want. But once you have it, it's a simple copy and paste (assuming the same text keeps reappearing).
You'll need to use video track2 or higher for the messages so it overlays on the video on tracks 1a/b. You can also use the alpha channel on video 2 to get your text to fade in/out. Use the rubber-band (may have to expand the track to see it) to get desired effect.