how to know the absolute start and end timestamps of each sentence

[nmadapan]

Here is an example.
[ 0 1] -4.637433 []
[ 2 38] 2.771251 welcome [welcome]
[ 39 53] 2.072704 to [to]
[ 54 111] 2.281620 animal [animal]
[ 112 175] 1.937740 today [today]
[ 176 206] 0.642767 []

How do we know the absolute start timestamp? The seconds displayed and the start and end frames do not sum up.