The statement is an attempt to underscore just how low the Italian morale was. Rommel had descended to the road to Luico (according to Rommel's naming conventions - the town is probably in Slovenia so its name is likely different today) and positioned a few men in the woods overlooking the road, and then captured group after group as they rounded a bend. With just five men to help him (three riflemen and two officers), he captured 1500 men. Obviously, if those 1500 had the will to fight, they could have overpowered his group.

The wikipedia entry on Rommel details the Matajur total:

During World War I, Rommel fought in France as well as in Romania (see: Romanian Campaign) and Italy (see: Italian Campaign), first in the 6th Württemberg Infantry Regiment, but through most of the war in the Württemberg Mountain Battalion of the elite Alpenkorps. He gained a reputation for great courage, making quick tactical decisions and taking advantage of enemy confusion. He was wounded three times and awarded the Iron Cross, First and Second Class. Rommel also received Prussia's highest award, the order of Pour le Mérite, after fighting in the Battles of the Isonzo in the north-eastern Alps on the Isonzo river front. The award was for the Battle of Longarone and the capture of Mount Matajur and its Italian defenders, which totalled 150 officers, 9,000 men, and 81 artillery pieces. In contrast, Rommel's detachment suffered only 6 dead and 30 wounded during the two engagements, a remarkable achievement.

For whatever reason, you have to look at the Battle of Longarone page to get the additional 10,000 men. I believe that the reason for this is that the Matajur 9,000 were captured solely by his portion of the Württembergisches Gebirgsbattalion (just over 100 men), whereas the Longarone follow-up capture of 10,000 men involved some Austrian "k. und k." troops.

http://en.wikipedia.org/wiki/Longarone

It's well-documented. The German Army did not give out Pour le Mérite medals freely.