If its already chilled I would just go with the 48 and count it as an experiment. If you really want the 1.058, you will 1.13lbs of DME. Probably should boil on the stove top with some of your chilled wort, rechill it and add it to your fermenter.
Goal points = 58 x 5 = 290
Current points = 48 x 5 = 240
290-240 = 50
DME = 44ppg
- 50/44 = 1.13