Hi there, Ana!
It's always better, in my opinion, to err on the side of caution when you are working within a specific time window. Likely your meal at
Mama Melrose's (and please, please try the Fresh Mozzarella and Vine-Ripened Tomatoes ... mmmm) will not take two hours, but the Cast Member who made the reservation has built in time on either side to accommodate a possible wait upon arriving, and any lingering over coffee (and the subsequent travel to Fantasmic!) thereafter.
Normally, you are seated fairly quickly when you have a reservation, but it is possible that circumstances beyond anyone's control are resulting in slight delays in seating parties.
And on the flip side, you definitely want to ensure time to get from one location to the next.
Enjoy your meal, knowing that you will have plenty of time to savor the company and the food, all without stressing about hitting your next time-milestone.
See you later, celebrator,
-Deborah B.