I am setting up the Door Game Mega slots currently local just to get itworking. In the Mystic Config. for door games I have the game set up as DD ( Exec external program ) and the data line calls the path to a batch filemega77.bat %3
Your setup looks right if you just wanted to run it locally so I am not sure exactly what is happening.
I am assuming you're using Windows 32 -bit based on the .bat file and that Mega Slots is a FOSSIL door? If you wanted to complete the setup for local/remote/all nodes it'd probably look like this:
Command: DX (Exec w/ DOSXTRN)
Data: cd<c:\doors\mega> mega.exe %Pdoor.sys
This assumes you're using Version 1.12 A47 though and you have copied the DOSXTRN files into your root directory.
This basically tells Mystic to switch to the c:\doors\mega directory and then run "mega.exe %Pdoor.sys" where %P is replaced by the path where that node's drop files will be created. No batch files or anything else needed.
I don't know the MegaSlots door in particular so I am just typing this based on what I read in your message.
--- Mystic BBS v1.12 A47 2020/12/04 (Windows/64)
* Origin: Sector 7 | Mystic WHQ (77:1/138)