1) create a single named named range called Game_Type which is defined as =Nerves_Data!$A:$A

2) Apply Data Validation settings to the Day of Week Analysis sheet cell B20 as:

Allow: List
Source: =OFFSET(INDEX(Game_Type,MATCH($B$19, Game_Type, 0)), , 1, COUNTIF(Game_Type, $B$19), )

That should do it.