why does my account value keep going down?

I am still fairly new to steemit and have put up a number of different posts - knitting, baking, garden, animals ... but only get a few if any upvotes, but I am not worried about that. But when i go to my 'wallet' and look at the value of my account it has gone down several times despite clicking on transfer rewards which appears at the top of the page. I is not a large amount but surely it should slowly go up not down?