Answer: $35$ numbers
$\sqrt n $ is less than $1$ from $9$
$\sqrt n$ is between $8$ and $10$
$n$ is between $64$ and $100$ (but not $64$ or $100$)
$65,66,67,68,...,99$
$\underbrace{\underbrace{1, 2, 3, ..., 64}_{\text{64 numbers}}, 65, 66, 67, 68, ..., 99}_{\text{99 numbers}}$
$99-64=35$