Camera [Q] Galaxy Tab 7.0 3 Video Camera Issue

My wife likes to use the Galaxy Tab 7.0 v3 (Sprint) for videos. Yesterday, when trying to take a video, a message stating she had ONLY???? 4032 MB (4 GIG) left in internal memory prevented her from taking a video several times. Yes, 4 GIG not 4 MB or 4 KB. I had installed a 32 GB SD card which she had never used, as the Sprint Model is a 16 GB memory model. Anyway, last night when I changed the default for storage (to find that you have to scroll down a settings menu to find the storage option...not very intuitive) of Camera/Video to the external card, the message stopped so the immediate problem is solved. However, why would such a message show up (I'm ok with that if there is insufficient space left) and prevent the video from operating, when there was still plenty of storage? Most of her videos are around 200 MB with her longest around 650 MB. Anyone have an answer? I could not find this issue addressed anywhere on the internet or Samsungs site.