Light End Dragon: If “Light End Dragon” or “Dark End Dragon” activate their effects, but an effect like “Shrink” is chained, so that when the effect resolves, they have less than 500 ATK or DEF, you cannot reduce their ATK and DEF by 500 to resolve the effect, so the effect is not applied.
When resolving the effect of "Light End Dragon", "Dark End Dragon", etc., if the ATK/DEF of "Light End Dragon" etc. has become less than 500 (such as due to "Shrink"), its ATK/DEF are not decreased and the effect of "Light End Dragon" etc. does not apply. Also, even if the opponent's monster is no longer on the field when resolving the effect, the ATK/DEF of "Light End Dragon" etc. are still decreased by 500.