New to having a pool. Not understanding this concept... Saltwater pool. Went to the pool store with a water sample and was told my pH was 6.8. I was given something to raise the pH (should be 7.2-7.6) and alkalinity boost. I asked why I was given 2 separate items, as I understand that raising my pH will raise the alkalinity (>7 alkaline, <7 acidic), and was told they were 2 separate things. What am I missing here?