My advice is to write whatever you want to and worry about the length later. While most of the site’s top storygames are extremely long (over a hundred thousand words), there are shorter ones which are very highly rated too. I personally admire writers who can tell a compelling, cohesive narrative in a few words.
What matters most is that your story’s length fits its scope. For instance, trying to write a larger story where a shorter one would suffice means you’ll have lots of unnecessarily wordy paragraphs or filler text that the reader would get bored skimming through. On the other hand, if you planned for an epic with multiple branches and parallel character arcs, trying to reduce your word count may mean the plot appears abrupt with too many under-developed elements.
Either way, best of luck with whatever you decide to write next. There’s also a contest going on too, if you're interested in getting guaranteed feedback: https://chooseyourstory.com/forums/news-and-updates/message/30125