The answer depends on your volume. In order to understand how to do this you need to understand how total points works. To calculate total points in wort: 1000*(gravity - 1)*volume. Basically, just keep everything on the right side of the decimal point * volume. Also, for hot wort, you need to correct for temperature (3-4%). This gives you a number that represents the total amount of sugar in the wort.

So, what you do is calculate the desired total sugar using your recipe data, then calculate your actual sugar. SubtrCt your actual from desired. That tells you how many points you need to add. Dme adds 46 points per pound.

For example:

Target preboil sg: 1.052

Target volume: 7.5 gallons

Target points: 52 * 7.5 =390 pts

Actual sg: 1.049

Actual volume: 7.6 gallons

Actual points: 372 pts

Needed pts: 390-372 = 18 pts

Needed dme: 18/46 =6.2 ounces