Handicap Calculation for Dan Grant for Week 20

Week of Rounds Used:		14	13	12	10	8		Total		Average		90%		Rounded to:
Gross Score:		64	61	59	60	53		297		59.40
Hdcp Score (over Par):		23	24	22	23	18		110		22.00		19.80		20

What does this mean? How are handicaps calculated?