Hi there!
In word form, 0.001 in worded form is one-hundredth.
Not actually a hundred, like, 100, but hundredTH, the TH meaning AFTER the decimal place.
This is just like how 0.01 is one tenTH, not ten like 10.
I am just saying that numbers after the decimal point will always end in TH.
Hope this helps!
Message me if you need anything else! I'd be happy to answer more questions you may have! :D