Spoke Length Tech Question

Building a wheelset and using WTB KOM Tough i45 rims with an ERD of 572. When I used a spoke calculator online the only rim size it had was an i40 with an ERD of 571. It gave me spoke measurements for the rear wheel of 578 right and 577 left. I'm wondering since I'm using the same style rim but in i45 can I still use the same spokes given the ERD is different.

My second question is... I only have 276mm spokes. Can I still use this even though it specifies 277?

Thanks