Corridor with different sized shape for template drops

This seemed like a simple question that someone has definitely asked before but I can't seem to find the answer to - I apologize if this is a common question.

When creating the corridor model - as I drop template through different interval of station, why do I end up with different shape sizes? I don't recall any of the prompt to cause the template to act differently. See attached image (white is the border of the template).

Thanks,

Dick