mmmmmm..
until you get an Ofsted Inspector who using the 1:4 and 1:8 says you cannot have a 2yr old counted in a ratio with 3 year olds which is in effect what you are doing... they do however sometimes say Ok to to have a 3year old in a 2yr old ratio,
In above example you would not have correct ratios using their criteria.. not point counting.. Had this happen to a friend
You would need more staff to ensure correct ratio.. you would be either 1 under 3 or 3 over 3s over.. ( a few too many overs but get my drift?)

Watch ratios carefully not just point counting... if unsure always ring Ofsted to clarify and check your ratio is correct..then you will have some back up if an Inspector takes this approach.
I would rather ensure it was correct than chance it.. and have someone turn up and then discover you get a poor inspection because of it.