周全 is a stative verb (s.v.) meaning 'thorough' or 'comprehensive' — used to describe plans, preparations, or analyses that cover all details. The dictionary also lists a traditional verb sense 'to help someone achieve a goal', but that usage is less common in modern Mandarin and falls outside the stative-verb category here. You'll most often hear它 as an adjective-like state: 计划周全 ('thorough plan'), 考虑周全 ('carefully considered').