Well, honey, four hundred and six thousandths in a decimal is 0.406. It's as simple as that. No need to make it more complicated than it is.
0.664
Four hundred six and sixty-four thousandths
0.604 = six hundred four thousandths.
76.402
0.0604
The numeral is 6.00409 (the decimal value is 409 hundred-thousandths).
6.00409
0.664
It is: 4.006
6.409
609.004
Four hundred six and sixty-four thousandths
401.206
Four and five hundred six thousandths.
0.604 = six hundred four thousandths.
76.402
206.0004