There is a fraction form and decimal form. The decimal form would be the same: 8.517, but the fraction form will be 8517/1000 since the 7 ends on the 1000's place, so you can remove the decimal and put it over 1000.
Decimal form: 8.517
Fraction form: 8517/1000
Also another fraction form is having mixed numbers: [tex]8 \frac{517}{1000} [/tex]