Does it say 11 spaces under 8 or 11 EYFS spaces? If you are working with 2 assistants is that full time or part time? Normally spaces are regulated by how many staff in at any time, your own family members and the space you have. I would say that you could have a total of 11 children plus your son under the age of 8 at any time due to space restrictions, as 11 with 3 staff doesn't work. Does that help?
I thought they had ditched the rule that said a childminders own children were always included in the ratios? So if your child was off the premises with another adult they weren’t the childminders responsibility? So, on that basis, I have no idea where they have got 11 children from. It’s a really odd number, can you query it at this point?