Strength and Justice have exchanged numbers, and knowing which system a deck belongs to is the difference between reading it and guessing at it.
In the older Italian and French patterns, Justice is VIII and Strength is XI. That is the arrangement in the Marseille pattern and in most decks descended from it. The Golden Dawn reversed them, and Waite followed, so that in the Rider-Waite-Smith deck and the very large family of decks modelled on it Strength is VIII and Justice is XI.
The reason is astrological and specific. The order's system runs the trumps against the zodiac in sequence, and it wanted Strength to fall on Leo and Justice on Libra. With the older numbering the signs land the wrong way round. Swapping the two cards fixes the correspondence table at the cost of altering a numbering that had been stable for three centuries. Waite made the change deliberately and Crowley kept it, renaming the card Lust.
There is a minor historical footnote: the fifteenth-century Sola Busca deck also places the strength figure at the eighth position, so the arrangement is not unprecedented. That is not evidence that the Golden Dawn was restoring anything, and it should not be presented as such. It is a coincidence of one unusual deck.
The practical consequence is that any table of correspondences, any book, and any statement about "the eighth trump" is ambiguous until the system is named. Both numberings are in wide use today and neither is wrong, but they cannot both be applied to the same deck. This is the clearest available demonstration that the tarot's occult apparatus was assembled rather than inherited: a scheme built in the 1890s required two cards to change places, and they did.