In the previous screenshot you plotted an area Graph. While this section is meant only for Gauge Graph. The image sample of the graph is already provided in the module.
The analogRead() reads a value from an analogue input pin and returns a scaled voltage measurement. The microcontroller translates the voltage readings into numbers ranging from 0 to 1023, where 0V has a value 0 and 5V equates 1023.
Thank you @meghad404 .
Also to add to @meghad404 's response, in here 1024 = 2¹⁰. Which refers to the 10 bits of 1s and 0s.
We have more such explanations from the fellow Bolt IoT Community Members over here -