 In the quotation Speusippus tells us that the number 10 is ‘perfect’ or ‘complete’. The explanation in Euclid vii Def. 23 (Heiberg/Stamatis 1970 p. 105; Def. 22 in Heath 1926 p. 278) for the phrase ‘perfect number’ is ‘number that is the sum of its proper divisors’. This makes the first perfect numbers 6, 28, and 496: 10 is not a perfect number in this sense. Rather, Speusippus appears to be speaking of 10 as ‘perfect’ or ‘complete’ in a way that fits with his claim that completeness is not there in the beginning but only comes on once the universe has proceeded a certain way, in particular, far enough that we can speak of numbers. What he means can be illustrated by a single example.