Hi and welcome to Digi Forums
The 2 wholes are intended to be used with the DIN RAIL bracket accessory: https://www.digi.com/products/models/76000682
The 2 holes are for M3 screws: M3 .5X6
If you have any further questions, please contact our support team: https://www.digi.com/support
Regards
Alex
Digi Technical Support Engineer