What is the HTML5 streaming video subtitle file extension in this specific case

[alienvi]

I'm watching video streamed via vzaar.com (uploaded by futurelearn.com)

I'm able to see the transcripts in the below format which plays fine with video in web browser

 

0:01 (Skip to 0 minutes and 1 second)
Neural Networks are a class of models which draw their inspiration from neurobiology. These Neural Nets are arranged in a way which is somewhat analogous to how real neurons are connected. Just as real neurons fire after reaching a certain activation threshold, the individual nodes of a neural net each represent an activation function triggered by a certain level of input.

0:26 (Skip to 0 minutes and 26 seconds)
The seminal paper on neural networks was published in 1943. In this paper "A logical calculus of the ideas immanent in nervous activity" Warren S. McCulloch and Walter Pitts attempted to map the logic of neural pathways. Research on Neural Nets was dormant for much of time since their inception but there has been a dramatic resurgence particularly in the last decade. This has been due to both emerging big data sets, as well as increased processing capacity which has made it feasible to train these deeper network architectures and demonstrate the impressive potential that neural networks can achieve. A neural network is arranged in layers. The first layer contains the input vector, one node for each input variable in the model.

1:20 (Skip to 1 minute and 20 seconds)
Then come one or more hidden layers, which can each have any specified number of hidden nodes. The final layer is the output layer, ....

NOW
I'm able to download the video
I"m able to find the transcript in the above format as text

question:
what file extension, I should save the transcript , so that when I play the downloaded video offline, the transcript works
(the transcript format is different, so .srt doesn't work)