Dear David,

Thank you for your question, and no you’re not being thick at all, this is a good honest question.

You’ll first need to look at the Direcimal square, this shows that the ‘teens’ have been removed which pulls forward the ‘twenties’ to create symmetry (as can be seen by counting down all four external-sides).

Taking the above into account, you can then calculate the new multiplication square as shown in this article where 4x4=26.

I hope this help clarify your question?