That's a good question.
The purpose of the checklist is to give you an idea of what your child knows. Mark up the checklist however you need to.
There is a 3-step process to learning - Introduction, Recognize, Identify. You have already introduced the concept and your child can recognize the shapes. With time, he will be able to identify as well. This process varies from child to child and concept to concept.
For more on this 3-step process, read this -
www.abcjesuslovesme.com/getting-started/...ce-recognize-identfy
Hope this helps!