Familiarity level and Proficiency level

Hello,

I am new to Khan academy and I have noticed while browsing through third grade math content that for each skill set within an individual concept like 'Strategies for adding two and three digit numbers', there are 4-7 problems. Is this enough practice for a student to claim 'familiarity or proficiency'? I realize there are other check points along the way such as quizzes and unit tests for more practice. Are quizzes and unit tests larger sets of problems?

I initially submitted this question under the 'how to use course mastery video'. Is this a better link to post product questions?