In the context of the scenario you described, the initial value represents the amount of gas in Joaquin's car at the start of the trip, before any distance has been traveled. Typically, if the graph shows the amount of gas (y) as a function of the distance traveled (x), the initial value would be the y-intercept of the graph.
If the graph starts at a certain point on the y-axis when x is 0 (meaning no distance has been traveled yet), that value indicates how much gas is in the tank at the beginning of the trip. For instance, if the initial value is 100 (assuming the units are in gallons or liters), it means that Joaquin starts with a full tank of 100 units of gas.
This initial value is important as it sets the starting point for how the amount of gas decreases as the distance traveled increases.