I’m not sure if spelt works the same but with my AP flour starter, my “stock” is approx. 300 grams/ 1 1/2 cups. When I feed, I remove half and add 75 grams water (1/3 cup), 75 grams flour (1/2 cup).
Usually I make a levain (leven, wild yeast sub for commercial yeast) of 1 Tbsp starter, 75 g water, 75 g flour and let that sit overnight or 8-10 hour until bubbly and passes float test although at this point I don’t check for float as I have confidence in what it should look and feel like.
I keep the discard starter and make Melissa’s sourdough naan, sourdough-masa tortillas, or crackers. You can use the discard in anything really - anything that has flour and water. For example, my starter is 100% hydration so if I have a cup of starter, I remove 1/2 cup flour and 1/2 cup water from whatever the recipe total is.
Bottom line, you do need to discard and use in something and refresh your starter with new feeding(s). You can search on “why discard starter” to see why. From memory, I believe there are ph reasons for one.