Sorry Bob I should have said one name - you're correct. Still it's a useful thing to know and in theory it should work for longer periods - after all if the Muni offer the search service then in my opinion they should return all likely finds for the one name for that period.
I accept that if I reckon my individual would be aged between say 50-60 then I'd hardly expect them to send me finds for someone aged 10 and I have at least included that information in previous searches but there's no clear guidelines on their site regarding this hence the ambiguity with the search service. After all we all know how, for example, ages can vary in censuses, certificates, etc and the information was only as good as given by the informant so for us we very often have to look at all targets to rule out before we can rule in?
In my opinion they should make the fee cheaper when quoting a certificate number as the searching has already been done by us the researchers. It wouldn't solve the issue of what is exactly included/covered by the search service however?