I have a different question. Why the heck are you using a Camry engjne description to service your xB when Toyota went through all the trouble to create a separate owner’s manual as well as to put the Scion engine’s fluid capacities on stickers in obvious places for easy reference?
1/2 qt up or down won’t hurt anything. But if you continue using the wrong information you’ll inevitably make a mistake. And it might be costly. For example, the same engine might use a turbocharger in one application and require synthetic, and not use one in another application and not require it.
I recommend that you simply get the correct manual and follow it.