This solution of salt in water not only will aid in drawing out the bitterness of olives from the tree, but it is also concentrated enough to preserve the olives as they're curing and after, in the jars they are stored in.
If you find that the olives are too salty for your palate after they are cured, you can always take them out of the solution, drain off the brine and place fresh water in the jar. Leave for a couple of days and the olives should have had their saltiness drawn out of them. Keep them in the fridge if you do this until they are all consumed.
MAKING A BRINE SOLUTION FOR CURING OLIVES