What are the fields: Egg Seed and Legendary Seed exactly here for?(I'm new into this program and RNG,sorry if that's already been asked )
I think going to r/pokemonrng will help you out, find the wiki guides on the side of the page, as well as using this fantastic tool.
http://gbatemp.net/threads/wip-pokecalcntr-iv-and-nature-overlay-plugin-for-sun-and-moon.460524/
Short version, they determine frames that you can hit to get the pokemon designated to each frame. I think it's a long process to explain, that's why the subreddit and the linked thread will help you more than I could.