Shorts

Can someone explain what happens with shorting. A couple of times in the last month the number of SRL shorts have dropped from around 2m to 1m. Soon to be followed by an increase back to just under 2m. I would assume a bit of in house juggling to make the end of year financial figures look good. So around 2m SRL shorts were covered but over this period new short contracts were written for close to the same number.
Neither of these transactions seem to appear in daily sales volumes which causes me a puzzle. But a lot of shorting practices puzzle me. I thought shorting was selling share you don't have or have "borrowed" (with a time limit) and then needing to buy them back to cover the shorted shares.
With SRL I assume it is a person/org that has an intimate knowledge of the company and that there finacial position over the past few years has improve a lot more than mine.
Hoping further discussion will help me understand how the game plan played. If the goal is to make money it seems to work.