At the time the school performs the inventory check, you or your family member must be at your house, in order to leave a signature on the form. If there is no one at your house, the school will consider/regard that you agreed to the result of inventory check.

Do the following sentences have the same meaning?
Not every customer is right.
Not all customers are right.

Please let me know the difference between following two sentences.
He doesn't know everything about that field.
He knows nothing about that field. **