There were nine Crusades undertaken to reclaim Jerusalem, unless they're not counting the Fourth Crusade which didn't make it past the plundering of Constantinople, but if they don't count the Fourth Crusade then they shouldn't count the Eighth Crusade either, which ended up in Tunisia..
Maybe they're combining the 5th/6th or the 8th/9th.
Point well taken. The fourth crusade was certainly a disaster...an attack on fellow Christians with no precedent... An attack which forever weakened the ability and resolve of Byzantium to absorb the shocks of the Islamic hordes.