That'll return 20 volumes matching the text "thunderbolts", but the original 1997 series doesn't appear at all. The one-shot annual from 1997 is the only thing from that year in the results.
I'm not sure what the solution is. More results by default? There will probably always be an edge case where the one thing you're searching for happens to be outside the limit. One solution might be to order the results by string length before returning them. That way anything that *exactly* matches "thunderbolts" will be the top results.