Right.
p. 171 points out that Pact is the magic skill which allows access to Divine spells, based on how much POW the worshipper dedicates, which depends on the worshipper's Rank:-
Acolyte - 25% of POW
Initiate - 50% of POW
Priest - 75% of POW
High Priest - 100% of POW
p. 173 next states:-
Casting Divine Magic
Divine Magic spells are prayed for by the worshipper before they can be called upon. Each Divine spell takes up a single point of Dedicated POW to store.
So there's your answer: one spell per point of dedicated POW, up to 25% of the worshipper's POW, rounded up. If your Initiate had 16 POW, he would be able to access four Divine spells.