Decimals or minutes. The professional standard is pretty much hours and tenths- ie 2.4.

Block time is logged in minutes (2:28), then converted to decimal points (2.5).

Here's a good scale to use:

0-3 minutes = .0
4-9 = .1
10-15 = .2
16-21 = .3
22-27 = .4
28-33 = .5
34-39 = .6
40-45 = .7
46-51 = .8
52-57 = .9
58-63 = 1.0