That's actually a LOT.

It means that, out of 181 potential economy passengers, 13 have:

a. OneWorld Emerald or Sapphire status; or
b. Fully flexible fares;
c. Have paid possibly 10% or more of their fare in addition, just to choose a seat.

Not everyone in a. and b. even bothers to book a seat when they're entitled to.

That's before you take into consideration those who haven't booked yet (nearly three weeks out, that could be quite a substantial number), and those who have booked but will end up being rerouted (OK some of those 13 could be rerouted onto another flight as well).

Overall availability is

F3 A2
J9 C9 D9 R7 I1
W9 E9 T5
Y9 B9 H9 K9 M9 L9 V6 SC NC QC OC G0

So F is pretty full, J has a reasonable amount of space but isn't empty, W is reasonably empty (half full at a guess?) and economy has plenty of space available but G, for the lowest fares, isn't available, and the N/S fares that represent the bottom of discounted (but not super-discounted) economy have closed (though this could be due to advance purchase rather than selling out).

Even then at least 3 V-class fares have been sold, so while it probably won't sell out altogether, it will be a pretty busy flight - don't expect empty middle seats!