Okay, so let me lay out why I'm suspicious of those numbers in the context of the article. The paragraph before that states:
>The number of deaths from coronavirus in Iran is nearly triple what Iran's government claims, a BBC Persian service investigation has found. The government's own records appear to show almost 42,000 people died with Covid-19 symptoms up to 20 July, versus 14,405 reported by its health ministry.
Now those two things aren't the same - the number of deaths of people who could possibly have had coronavirus isn't the same thing as the number of deaths of people who were actually confirmed to have coronavirus. The first is a quite expansive definition which is what the BBC is using, and the second is the number the Iranian regime publishes. And that second definition is a perfectly reasonable thing to publish, it's what the UK publishes and reasonable people know that's likely to be an undercount.
Now, given that the BBC is already comparing apples to oranges, comparing the suspected cause of death with confirmed. Let's look at the claim you're quoting.
>The number of people known to be infected is also almost double official figures: 451,024 as opposed to 278,827.
So what I'd want to see, before I took the second quote seriously, is a defintion of what the numbers refer to.
Because if you read it in context, that sounds to me very much like it could be the BBC is doing exactly the same thing again, comparing the official figures which are the number of people actually tested confirmed cases, with the unofficial figures, which are simply people presenting with symptoms but not comfirmed.
Testing capacity is a worldwide issue, but apparently with Iran we're going to try and literally tie this to the Iranian revolution.