There is a lot wrong with the former director of the FBI saying "8647" in a very public statement. First, it confirms his deep vitriol for Donald Trump, which persisted even when he was head of the FBI.
Second, it shows that Comey would love to see Trump "eliminated" - clearly he is familiar with the assassination attempts on the President's life. Ask yourself, what adult man takes the time to arrange "8647" in sea shells to then publicly post this? That's pretty deranged for any adult man. Its particularly deranged for the former head of the FBI.
Third, it also serves to bolster what Kash Patel has been saying about James Comey and the Democrat Deep State operations against Trump. Comey was and is a really bad guy. He used his immense power to try and destroy a sitting President simply because he disagreed with his policies or personally didn't like him,
or both.