Over 10 years ago I raised ratio issue with a CCI (childcare inspector) and was told that ratio was the nursery as a whole. Over the years there has been some changes to ratio but it does not go as far as stating that there has to be x number of adults in the same room as the children. Instead it says things like "Children must usually be within sight and hearing of staff and always within sight or hearing." (EYFS Sept 2014).
Great nurseries I have temped in have had more staff than the minimum requirement. Layout of nurseries is also often planned such that things you do frequently (so nappy changes when you are talking about under 2's) are done such that children are still in sight and hearing, whilst still giving the child being changed some privacy.
Staff on a break or doing things like cleaning are now not part of ratio.
"The ratio and qualification requirements below apply to the total number of staff available to work directly with children." (EYFS Sept 2014)
So if a member of staff is doing admin away from the children, then they are not working directly with the children so should not be counted in ratio. Staff on a lunch break are not in ratio.
You felt it was wrong when you visited. You felt strongly enough about it to send an email. So really I feel you have decided that this nursery does not meet your expectations.
Is it typical of nurseries - well there is no typical. Some nurseries will manage things better than others, some will spend more on some things than other things. Some for example spend lots of making the outside of the nursery look nice, on latest equipment. Others spend it on staff. There has to be a balance, spending on staff and on equipment.
So keep looking at nurseries, find somewhere that has a better balance to how they spend the money. Also look at other options, such as Childminders.