Handicap Calculation for Mike Keating for Week 19

Week of Rounds Used:		15	3	1		Total		Average		90%		Rounded to:
Gross Score:		58	62	57		177		59.00
Hdcp Score (over Par):		21	23	20		64		21.33		19.20		19

What does this mean? How are handicaps calculated?
Handicap Projection for Mike Keating for Week 20

If your next round score is:		Your new Handicap will be:
63-68		17
69-73		18
74-79		19
80-84		20
85-90		21