Hi, It's a "free" day. When it's kept to one day it really works. I stretched it to 1 1/2 days too many times and put back on 5 -7 pounds so now I'm doing a mini reboot to lose it (meaning I'm in P1 for a couple of weeks and then phasing off).
But, yes, you can go all out. After one or two "all outs" you'll realize you really don't want all the food you once ate. My eating habits have changed (for the better). At chinese restaurants I get steamed dumplings and am satisfied and before it would be fried everything (crab rangoon, general tsos, chicken fingers etc).
Have fun when you get to have "fun"! You may want to post this in the "maintainers' thread. You're likely to get more responses.