rental & bank interest tax calculations

I have been trying to answer a practice question in Kaplan exam kit
its says James has the following income 14/15 of
rental income £12,200 bank int £8300 gilt edge security int £1500 interest on Nisa £1200

The Nisa interest is exempt I understand this bank interest grossed up to £10375 giving total taxable income £14075 its taken the £10,000 PA from the £12,200 rental income, leaving £2200 & £10375 (bank int) & £1500 gilt edge as assesable. The answer has taxed the £2200 at 20% and only £680 at 10% = £2880 limit (starting rate) . The rest £11,195 again at 20%
Why is the £2880 not taxed at 10% ? I am getting a little confused with the if and if only the savings income is in the first £2880 rule?

Many thanks in advance
Nicola