Time to send 32KB over 9600 baud serial?

Indeed but you have lost precision by multiplying your approximation of the bit width, such that then specifying the time to three decimal places is incorrect.

To avoid loss of precision, do not use a rounded intermediate expression, but rather:

bytes x bits_per_character / bits_per_second

So in your case:

32000 x 10 / 9600 = 33.333(recurring) seconds.

Traditionally however 32Kb refers to 32 x 1024 bytes, so in that case:

32 x 1024 x 10 / 9600 = 34.1333(recurring) seconds.

If you need to roughly check the magnitude (whether it's 3s or 30 or 300), remember that 9600 kbps ~ 1KB/second (10 bits if you have 2 extra parity/stop bits), so 32KB -> around 32 seconds.