Classic shirt – help needed re plackets

Hi! I've just downloaded the classic shirt pattern but am finding the right placket instructions confusing. It says to cut a 1 inch strip from the shirt front, then make a row of basting stitches 1/2 an inch from one of the long edges of this placket. This I understsnd. But the next instruction is to apply a 1x29 inch strip of interfacing aligned to the basting stitch, so that the interfacing js in the middle of the fabric placket strip. This doesn't make sense to me as both strips are the same width, 1 inch, so I dont understand how the interfacing strip can be seen in the middle of the fabric strip? The next instruction says to see this back onto the shirt front and its meant to be longer than the shirt front. However since the fabric strip was originally cut from the shirt front hiw can it now be longer than the shirt front? Has anyone made this shirt who can help please? Thank you!!