What does 1 Chronicles 21:17 mean?

David said to God, 'Wasn’t it me who ordered the count? I’m the one who sinned and did wrong. These people are just sheep—what have they done? Please, Lord my God, let your anger fall on me and my family, not on your people.' 1 Chronicles 21:17 - Modern Text Bible

(David takes full responsibility, asking God to spare the people and punish him instead.)