Set your location at the top — that's the one terminal every item's price is pulled from, so the whole order reflects buying everything in one stop.
Local (default) — uses your location's price. If that terminal doesn't sell an item, it automatically falls back to the closest terminal that does, clearly flagged (e.g. "Not at Admin - Nyx Gateway — nearest: …") so you know that one item needs a separate stop.
Manual — type in whatever price you're seeing in-game yourself instead. No live lookup, just tracking.
Your item list, quantities, chosen modes and location are saved only in this browser (localStorage) — nothing is shared with other members or sent anywhere except live price lookups to UEX Corp's public API.