You should follow these instructions if:
If you intend to hang your blinds within the window recess (sometimes called the reveal), you should measure the "recess size" which is the exact width and drop of the window recess. You should follow the instructions below.
When you enter your measurements, select size type as "recess size". Do not make a deduction! As you have given us the exact dimensions of the recess, we will make the necessary deductions so that your blind will fit perfectly into the recess.
Should you have any concerns when measuring your window, please contact us via e-mail (firstname.lastname@example.org) or on 0161 494 9616 (9am - 5pm Monday-Friday 9am-12am Saturday).