A special usage of AN

[duc]

Hello everyone,
Please look at this sentence :''AN estimated seven percent of British people are now vegetarians and there are a great many others who only eat meat occasionally.''
I wonder why they use AN here before percent because seven percent is accountable.
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[Haihao]

''AN estimated seven percent of British people...'' = A result made by estimation indicates that seven percent of British people...''

[Jamie (K)]

I think it's because "seven percent" is used in place of the word "number" -- an estimated number, the estimated number.

[Haihao]