It's used to convert METAFEES to BTS for the purpose of paying fees, since all fees are really paid in BTS.
You finance the funding of the pool by keeping the CORE exchange rate slightly higher than the going rate of the asset, so you make money from the conversion. Yours is currently set to 25000 BTS per METAFEES though which is a bit high.
Hmmmm.... If it's set too high, how did the pool run out?
50% of the asset creation fee is put into the fee pool, so METAFEES started out with 2500 BTS in the pool.
That's enough to pay for approx 60 xfers or 250 orders, and it appears it's reached that limit..
Since the CER is 25,000 BTS/METAFEES, you collect 0.1 METAFEES per 2500 BTS in pool spending.
If you were to set the CER to 2,500 BTS/METAFEES, then next time you run through 2500 BTS in the pool, you'll have collected 1 METAFEES in exchange.