These watch lists contain tickers which were the most traded by retail investors on Nasdaq at a given date (yesterday, 2 days ago e.t.c.). We never have data like that for the current market day (because it takes a while to compute them), that's why there are lists of "yesterday", "2 days ago" e.t.c. — up to 7 days ago.
Every list contains top-10 tickers and is ordered by activity. In example, if a Top Traded, 2 days ago, Retail investors list contains AAPL, MSFT, ZM then you can tell that AAPL was the most traded (by retail traders) asset 2 days ago, and retail traders activity on MSFT was significant yet still lower than on AAPL.
Important note: for these lists, "X days ago" actually means "X business days ago". So in example, if it's Monday then Top Traded, yesterday, Retail investors list contains top tickers traded by retail investors on last Friday, not Sunday.