You probably used a download accelerator which open several connections to the server to download different pieces of the files in parallel, so it got counted several times even though you downloaded it only once.
You already downloaded it at least once before when you first installed HikaShop.
When you download the install packages via the update menu within HikaShop it doesn't change that counter. The counter is just there to avoid abuses. If you go to 0 (which should not happen), you can always contact us to increase it.