This is the change in home value for a typical house in this market from 3 months earlier, minus any appreciation from general inflation, and then annualized (i.e. – multiplied four) to get an annual equivalent net appreciation rate.
Quarterly comparisons have more ‘noise’ in them and will tend to bounce around a lot more than annual comparisons. However, quarterly data can also spot market reversals and changes quicker because it only looks back 3 months, instead of a year.