Need Help Converting All-Grain Recipe to Extract

I am an AG brewer but I have a friend that is just starting to get into brewing extract brews. He has one extract batch under his belt and looking to brew another. One of his favorite beers is Ska Brewing Modus Hoperandi. I found an all-grain recipe for him, but I don't really know how to convert it to extract. Here is the recipe I found. Any help would be greatly appreciated. Grains:

Batch size: 5.5 gallons

12.75# Pale Malt (2-Row) US (87.93%)
1.00# Caramel/Crystal 90L (6.90%)
0.75# Red Wheat (5.17%)

Hops:
1.75 oz Centennial (9.10%) @90 min
1.25 oz Cascade (5.40%) @30 min
0.75 oz Centennial (9.10%) @30 min
1.25 oz Cascade (5.40%) @5 min
1.25 oz Columbus (13.20%) @5 min
2.00 oz Cascade (5.40%) @0 min
1.00 oz Columbus (13.20%) @0 min
3.00 oz Cascade (5.40%) (dry hop)
1.50 oz Columbus (13.20%) (dry hop)

Yeast:
White Labs WLP001 (California Ale)

 

Swap out the pale malt for 8.5 pounds of extra light DME, or 10 pounds of extra light LME. And make sure you do a late extract addition.

 

You can steep the crystal 90 but not the wheat. You can leave it out or sub a pound of the light extract with wheat extract.

 

Is the amount of LME typically more than the DME like that? Or is it something with this conversion in particular?

In other words why not 8.5 lbs of either LME or DME?

 

A portion of the weight of LME is its water content. 10lbs of LME has the same amount of fermentable sugars (approximately) as 8.5lbs of DME.