108 was a number.
According to Jo Grant, 98 plus 10 was equal to 108. Also according to her, 108 divided by 9 was 12. (TV: The Claws of Axos [+]Bob Baker and Dave Martin, Doctor Who season 8 (BBC1, 1971).)
In 2020, a Final Warning Missile, launched by the Judoon into Ruth Clayton's house, played a message that informed about the isolation of the house in 108 seconds. (TV: Fugitive of the Judoon [+]Vinay Patel and Chris Chibnall, Doctor Who series 12 (BBC One, 2020).)