Because of the point totals. The weekly total is as of the nightly total on Monday night, not as of the nightly total on Sunday night, which a Mon-Sunday total would be. Now there is world placement that comes into the figure. I see the updates usually hit about 9:30 pm Mountain Time, that makes it about 4:30 am GMT. Perhaps the ROTW server updates on a different schedule.
It's now Sunday Evening, the new top scores for the week will not be posted until tomorrow night's point process is run meaning any edits I do until just before the update process runs will be counted into my total for the week. And when the top scores for the week are totaled it will be higher than tonight's total will be.
And I go back to when I got the 500 mile bonus, if it didn't count Monday I would not have gotten it, as I got it when I added to my weekly commute 180 mile trip down to Southern Utah and and back up On Memorial Day last May. Without that 360 miles in one day I would have come nowhere near the total. And I got the Bonus a couple days later, before I'd driven enough additional miles for that week's total to get me to 500 let alone how I should have had to wait until that following weeks total was calculated.