Lying on a CV in order to get a job can be prosecuted under the Fraud Act (obtaining money by deception).
If when asked to your face "Bloggs, how many hours do you have?" you answered "over 500, Captain Pprune" that would be different to "500 hours, Captain Pprune".
So, on your CV/letter, put "over 500 hours". I can't see a lawyer getting past that.