There isn't really a standard for that. Every piano I've seen has a different key height, pedal position and sensitivity. Especially upright pianos suffer from some physical limitations. Also they need to fit players of every size. That's why many piano pedals are actually L shaped. It usually takes some time to get used to playing a piano for the first time.
Since digital piano pedals are not L shaped it is better to align with your foot to the most comfortable position and do not copy real piano measures directly. As a general measure, you should adjust it to your own standing position. It should be comfy to reach with a little effort without extending for it, but also shouldn't bother your foot while not in use. Sustain pedals are positioned a little right from the center. You can place it aligned with your right foot (or toe) in your standard position, a few centimeters ahead. Do also a Google Image search for "piano position".
Ah, also before screwing it to the floor, use double side tapes and play for a while and ensure the position is comfortable. There is no such standard, it is better that you play comfortably.
NOTE: I couldn't get the Preformatted text to work. Adding a crappy screenshot instead.