Subtitles are cut off

 I’ve only uploaded 2 videos but both videos have the subtitles cut off when i post them to Facebook and I am unsure how to fix this. 
I tried to upload a photo but this system won’t allow it. To give you an idea, the words float up towards the video from the bottom and a line cuts through the video and the words.  The words need to stay lower where they were originally placed during the creation of the video. 
Please help.