Hi there,
By using 1fr 1fr 1fr, each rows/child element will take one-third space of the width of the parent element .grid.
Each row will have the width of 400/3px;
Reply if it helps you.

There are not six rows but three. 1fr makes logical sense, so would be the one to use (and it is what the lesson checker expects, according to the message).

By using 2fr 2fr 2fr each row/child element will take up two-sixth space of the width of the parent element.
Each row will have the width of [(400/6) x 2], which again gives us the same results, hence my initial question.