Questions regarding the Appraisal Report?!

[Justin Brin]

In the appraisal report I noticed that the appraiser does adjustment in the comparable price depending on the sale date. How is that number calculated?
If the comparable property was sold 2 months ago then how much extra will he put? How are the adjustment calculated?

What about for sq.ft. how are the adjustment calculated if the comparable have different sq.ft.? What will be the formula?

What about for pool and spa?

I noticed the appraiser added $25K for pool and 10K for a spa. Where does he get those numbers from? Is it the average cost to build a pool in that area?