Listen for one thing on the first pass: can you repeat the brand line after the track stops? If not, shorten the lyric and move the brand name earlier. Adding more features rarely fixes a weak hook; reducing the message usually does.
The generator returns two versions because arrangement and vocal phrasing vary even from the same brief. Compare the opening three seconds, clarity of the name, and how naturally the tagline lands. Keep the better structure, then regenerate with one focused change rather than rewriting the entire prompt.
The 10-, 15-, 20-, and 30-second choices are real generation parameters, not words appended to a generic prompt. For broadcast or paid media, still verify the rendered file against the exact frame boundary and trim or master it if the delivery spec is strict.