The Short Form Rules dialog enables you to tailor the rules used to assign short forms when adding new entries.
Different rules can be applied to 1‑word, 2‑word and 3‑word expansions. For expansion with more than 3 words the initials of all words will be taken.
For each word the top and bottom rulers enables you to define respectively the number of leading and trailing characters the short form should retain. Selecting star in the top ruler means you want all characters.