Generally, we recommend consuming 1-2 servings of your protein powder per day. This is going to depend on the rest of your diet and how much protein you consume in total. If you are eating a healthy diet though and including protein foods at your meals/snacks, usually 1 serving is sufficient at helping meet your protein needs.
There isn't much benefit in consuming too much protein for the day. Your body needs a certain amount and it's really important to get enough, but at the same time going overboard isn't helpful. However, if you consume a decent amount of protein at once, it doesn't all go to waste. Your body is pretty efficient at storing amino acids and slowing down digestion if you consume a larger amount of protein at one sitting.
You shouldn't be as concerned about your protein intake at once, but more so over the entire day. Your daily protein intake is going to be more important. Of course, though we wouldn't suggest consuming an astronomical amount of protein at one time. A lot of people experience digestive issues from getting too much protein at once, or in a day. If you consume two servings at once, it's just more likely that you are probably eating too much protein in total for the day.