King 4000x stone ???

Hello

I am looking to add a fine polishing stone to accompany my newly acquired Shapton 1000 and came across this King 4000 stone that the price is too good to pass up (in Canada of course).

https://www.leevalley.com/en-ca/shop/tools/sharpening/stones/56542-king-4000x-water-stones?item=60M0303

it is listed as a 4000 grit but one image says 6000 and every where else that I have checked s series stones from king were 6000.

any ideas why this might be ??