Inaccurate shower door sizes on the website

Recently I purchased a corner entry shower door from iTILE Northriding branch. The measurements on the box are 900x900x1800. The floor was tiled to this size. Upon installation of the shower door, it was discovered that the correct measurements are 880x880x1800. This caused the tiles to be chopped up, and replaced, requiring me to buy more tiles, and pay the tiler extra for his labour. I called the branch to complain and their response was that they round up the sizes to the next big number. This is unacceptable, as this statement is not indicated on their website. The question is who is going to pay now for my extra cost, which I did not anticipate for? I am inserting a link for proof: https://itile.co.za/product/090-clrchr-corner-entry-shower-900x900x1800/