Make sure you're in Timeline view rather than Sceneline view. That way you can see what's going on.
The black video clip will be on the Video 1 track. The title will be on the Video 2 track above it as a separate clip.
By trimming, dragging or extending the title clip, you can make it shorter, longer or make it begin and end at any point in your video.
Possibly an easier way to do what you want is to not use the Black Video beneath your Titles. So long as you do not change the background of the Title, you will get black.
Now, in Timeline View Mode, use a small segment of Black Video. Normally, I start all Timelines with 02 sec. of Black Video for a couple of reasons. I create the Black Video (New Icon>Black Video) and then Dbl-click it to open it in the Source Monitor. There, I set the Out Point, so that I get 02 sec. Duration. I drag this to the start of the Timeline. Then, create you Titles as needed, and place them behind the Black Video on the same Video Track. If you wish another Title Duration, than the default, in Edit>Preferences>General, set the Duration for Still Images (note - this is in Frames, so you might need to do a bit of math). Between your Titles, use the Dip-to-Black Transitions. You will get the same effect as having the Titles over Black Video.
Hope that this is what you need, and that this helps,