Personally, I always measure my yield right after salting and only look at other yields for a rough idea. The main thing is to track your yields over time with the same recipe and milk. I've said this before, but for me it takes at least 5 times making the same cheese before I even *start* to get a good idea of what I'm trying to accomplish. I think as one gets more experience it gets easier, but I wouldn't be setting any metrics before you've stabilised what you are doing.
Quick note on metrics - There are 2 related concepts. A "measure" is something you measure. It can be anything: temperature, pH, time, amount, whatever. A "metric" is a measure that you use to modify your process. When you are doing something for the first time, you should have no metrics, only measures. It's OK to vary the process and keep track of how that affects the measures, but you shouldn't be trying to set targets on metrics until you have really dialed in your process. I'm guilty of speaking really ambiguously given that I'm always talking about pH targets, consistency targets, and even yield targets. Just keep in mind, that I'm pretty loosey-goosey with my "targets" for a very long time. I generally have targets so that I can take measures, not so that I can adjust my process.
For example, you might have a flocculation multiplier target. You can change it with the idea of simply trying to measure how it affects other things like consistency, yield, etc. However, until you are getting pretty close to achieving your ideal goals, you wouldn't start adjusting the flocculation target *in order* to inch closer to a better yield.
To be more specific to this case, whatever yield you get is fine as long as the cheese turns out fine. You should measure it and record it for later, but for now, you shouldn't use it to control anything. If the cheese doesn't turn out fine, you probably still don't want to use yield as a metric. Instead, adjust your targets in other places, but still record the yield. Later, when the cheese is turning out well, you can use the yield to help you decide if there is something else you might do to improve. For example, you might think that too low a yield implies that maybe you can afford to have more moisture in the curd and give it a try. At this stage, though, that's not going to be controllable.