8-month-old Lucas is brought to the clinic for a routine check-up. His mother reports that he has started crawling and can sit unsupported for a few minutes. Lucas’s mother is concerned about his progress, as he has not yet started standing with support, which some of his peers have already achieved. The nurse documents the following: “Lucas is 8 months old and has achieved the milestones of sitting unsupported for short periods and crawling.”