I'll simplify it for you. The arbiter says this is what I think is a fair outcome (tentative statement). The arbiter wishes to see if there are any objections from either side and what the basis of those objections are. Then decides if those objections have validity and if his initial decision needs to be modified.

An arbiter's job is to try to come to an amicable decision if possible and what he considers fair if not. Which is why a tentative decision is a good step to take. The binding part of an arbitration is only binding when the final decision is made by the arbiter.