Day of the week edge shows differences in your behaviour by day. We all have our good days and our bad days. It is possible that your lifestyle or the markets are better for you on different days.
If you have a positive or a negative edge on a particular day, you need to examine what goes on that day. Do you work from home on Wednesday, so you are distracted? Are you excited on a Thursday because your favourite show airs that night? Assess your emotions and environment on each of your trading days to understand the full picture of your trading.
It is worth knowing which day you are best and which you are worst, and make changes to your trading schedule when appropriate.