Video File on SD Card After Hiding Reduces Phones Memory

[vishnuvpat]

I am using HTC M8 and my issue is with hiding video files. For hiding video files I am using gallery vault app. The problem is that I have a video file (wmv format) 1 gb in size on my SD card and when I try to hide the file using gallery vault or any other video hiding app the video file reduces phone memory. I was told that when a file in SD card is encrypted it is getting stored in the same destination (SD card). For eg. a file in SD card would remain in SD card even after hiding. So why does the files which are hidden is reducing my phones memory. I had the same problem with my S4 phone.
Can anyone provide a solution to this Problem