Interpreters always work in teams of at least two people during a conference, since the process of simultaneous interpreting requires utmost concentration and is extremely taxing, which is why it cannot be kept up for any lengthy period of time without quality suffering at some point. Therefore, interpreters take turns at the microphone every 20 to 30 minutes. However, this usually does not mean that the colleague who is not actively interpreting can unwind completely and go take a break. Instead, he will continue to listen to what the speaker is saying in order to be able to support his booth partner if necessary.
This support is especially appreciated by the active partner if the presentation contains many names and numbers. Because when interpreting simultaneously, one has to be able to listen to what is being said, to remember sentences and context and to repeat them in the other language while one is already listening to the next sentence, but complicated names and numbers in particular have a tendency to get lost during the process.
Let's take the following sentence, for instance.
"Last year, our company's net sales grew by 8.7 per cent to 156,483,707 Euros."
Here, the interpreter is able to grasp that net sales have grown for that company, and perhaps he is even able to remember the 8.7 per cent, but as complex a figure as "156,483,707" is almost certainly lost. Were the active colleague alone in the booth at this moment, he would most probably have to limit himself to "some 156 and a half million" in his interpretation, if the exact figure is not also shown up on the screen.
The "resting" colleague, however, does not have to expend any capacities on the process of interpreting, but "only" on listening. Therefore he is able to grasp the entire figure and quickly writes it down for his partner on the notepad which nearly every interpreting team always has lying between them.
Thus, the active colleague can fully concentrate on the purely thematic content of the sentence, and once he comes to the point where the figure must be inserted, a quick glance at the notepad suffices for him to be able to repeat the exact sales growth figure.