The Position Statement is not a pleading and does not need to be as precise. It is without prejudice so it cannot be referred to later. However, it is your opportunity to explain your case to succinctly to the mediator and to show the mediator that you are on top of the case.
At the same time, it is also your opportunity to explain certain facts to both the solicitor acting on the other side and their client, especially if you consider that they have not understood your case. You can stress certain points in the Position Statement and, as the client will read it before the mediation, you can get the message to them.
It assists the mediator to set out who is attending and what offers have been made, if any.