Write the word form for each number and give the value of the underline digit 2.300 digit is 3

The number can be read or written out as

... "two and three tenths",

or as

... "two and three-hundred thousandths".

The latter form is tricky, because it needs to be distinguished from

... "two and three hundred-thousandths," which is 2.00003.

You would only use the form involving thousandths if you needed to ensure that the precision of the number were communicated properly.

The value of the digit 3 is 3/10, three tenths.