Be aware that when you have cleared customs, you will be outside the main terminal and will have to wait for UA ticket counter to open before getting back into the terminal. Based on a 10 hour layover, you might have 6 or more hours before you can get to the ticket counter, and with NAIA it is even possible you will have to wait outside as the entrance security might not let you back in so early. I say this in the hope you have the time to schedule something to do in Manila for a few hours instead of waiting outside. There is a shuttle bus to the Resorts World complex with restaurants and casino. Hope it goes well for you!