Let’s imagine it’s currently Wednesday the 1st. Does “next Saturday” mean Saturday the 4th (the next Saturday to occur) or Saturday the 11th (the Saturday of next week)?
In this context, a week is 7 days starting with the day you’re on. So if its a Wednesday, this week starts on that day and goes through Tuesday. On Thursday, this week becomes Thursday through Wednesday. Any day in “this week” would be “this $day”. After the last day of “this week”, we start next week and the days in that week are “next Saturday” for example.