1 o'clock

tan(45) - Wolfram|Alpha
2 o'clock sqrt(4) = 2

3 o'clock is simply a rounding of the value of pi equaling 3

4 o'clock is the result of log(55) in base 10 according to Wolfram Alpha

log(55) - Wolfram|Alpha
5 o'clock

x^2=3^2+4^2 - Wolfram|Alpha
6 o'clock

3! - Wolfram|Alpha
7 o'clock I'm guessing the rounding of 6.9

8 o'clock 16/2 = 8

9 o'clock 3x3=9

10 o'clock g = gravity constant of 9.8m/s/s rounds to 10

11 o'clock 0x0B is hexidecimal for 11 in base 10

12 o'clock 1100 in base 2 binary equals 1x8 + 1x4 + 0x2 + 0x1 = 12