It is my understanding that you are asking why the y-axis is displaying the values as strings such as 'first', 'second' and so on, instead of numerical values.
The first step is to understand the data that the scope is actually displaying. The scope is meant to display how the gear value changes with time. By observing the model, it can be seen that the scope is connected to the output signal from the Gear_logic Stateflow chart.
This chart models the shifting of gears based on throttle and speed of the vehicle. It calculates next gear value based on current gear, throttle, and current vehicle speed.
According to the chart, there are four states that can be reached - 'first', 'second', 'third', 'fourth'
These are the same values that are displayed on the y-axis of the scope output that you have attached.