You don't really understand this Betfair thing do you. The odds you see are what people are asking for, and with such pitifully small sums available the figures can be very misleading.
For example,, there is now £2, (yes £2) available to back +0.50%, and only £22 available on the other odds. So if someone wants to have £22 on a + 0.5% rise at odds of 9/1 (10 in decimal odds as displayed) then the appearance will be a massive swing to 100/1 on for that rise.