Hi Dlareh,
Thanks for the question! You ask a good question, and I'm glad for the opportunity to expand on this idea.
First, regardless of whether you look at this as Could Be True or Must Be True, it won't affect how you solve the question. So, it's nice to know that this issue won't affect your score.
The reason we say it's Must is that in LSAT LG, when something has an inherent, fixed aspect, then it is something that must be the case. Here we have a range of possibilities, but the endpoints (the maximum and minimum) are fixed. That makes those endpoints constant, and thus Must Be True.
For example, let's say that a variable will be placed in any of the first three spaces in a game. So, it
could be in space 1,
could be in space 2, or
could be in space 3. But, overall, it
must be in one of the first three spaces. That's an example of how a set of uncertain outcomes (which of the three spaces it is in) all fall under a fixed outcome (it's always in one of the first three spaces). This is also how Hurdle the Uncertainty works.
In that same example, it's also the case that the earliest the variable
could appear is space 1 and the latest it
could appear is space 3. Thus, it
must be the case that space 1 is the earliest it could appear. Right there is where it gets tricky—"it
must be the case that the earliest/latest it
could be is..." Ultimately, what we have here is that the endpoints of the range are fixed, and when that's the case, it's something that Must Be True.
Great question, and one that I've actually been wondering if I'd ever get asked
So, please let me know if that helps. Thanks!