You're correct in noting that the distance to the Andromeda Galaxy is often stated as 2.5 million light-years. However, it's essential to understand that this figure represents the distance based on the light travel time, as you mentioned.
The light we currently receive from the Andromeda Galaxy has traveled for approximately 2.5 million years to reach us. During that time, the galaxy has been moving closer to us due to the effects of cosmic expansion and gravitational interactions between galaxies.
The actual current distance between the Milky Way (our galaxy) and the Andromeda Galaxy is estimated to be around 2.537 million light-years. This value takes into account the movement of the galaxies over the time it took for the light to reach us.
Determining the precise distance and movement of galaxies is a complex task in astronomy, involving various observational techniques and calculations. However, it's important to note that these measurements are subject to some uncertainties and refinements as our observational techniques and understanding of the universe continue to improve.