98 was a number.
According to Jo Grant, 98 was twice as much as 49. Also according to her, 98 plus 10 was equal to 108. (TV: The Claws of Axos)
"Harold Saxon", after finding that Vivien Rook was not affected by the Archangel Network, admitted to his wife Lucy Saxon that its 100% effectiveness was more "99, 98..." (TV: The Sound of Drums)