WDMyCloud App Cache & Storage

I have the WD MyCloud app on my S2 Android phone.  It seems to work fine except I am trying to download a single file that is 1.5GB.  The app says it is unable to do so because of the size.  It tells me to clear my cache.  When I go to do that it tells me that some data will be lost.  What data?  The previous downloads?  Something else?

I also wanted to increase ther cache but it says there is not enough room.  I have an external sd card that is 32 GB and only half full.  I would like to store all downloads to that card all the time and use it for the cache.  How do I do that?

I was able to find out how to change the location of the download.  If I just hold on the file for a few seconds I click the 3 dots in the upper left hand corner and I can select “save to SD card”.  

What does “share” do in the same drop down menu as "save to SD card " is located on?