In the song, "69" refers to a sex position where two people pleasure each other simultaneously with oral sex. It also references the phrase, "ate." The word "8" in this line refers to cunnilingus, a term of endearment for one of the participants in this sex act. Drake has a long history of lyrical wordplay and this is no exception. He is a master at it and it pays off here.
The number 69 is a number with only two prime factors, 3 and 23. It cannot be simplified further using prime factorization so it is a square root. The square root of 69 is 8.30662386 (approximately). This is a very interesting fact and will make you think!