Digital numeric help

Brianna • psychic medium•Reiki Master•mama•wife💕 Facebook.com/bgspiritconnections Bcspiritconnections.com

So I have the ept numeric digital which tells you the numeric value of LH along with a yes or no.(30 and higher will read yes)

Yesterday morning I got a yes with a level of 59, in the evening I got yes with a level of 39 and now his morning I got 50.

Why did it go down lastnight and then back up this morning?