The charge is returning to a higher value after a high load, it's the approximation of the software which tries to measure the correct charge of the battery . If i'm reading the graph correctly , the spikes are immediately after you stop doing any activity, or after you play a movie/ game , browse the net or other activity witch drains the battery very fast. I belive that the software tries to approximate the rate at witch the battery discharges based upon the current drain, but if you stop immediately , the software tries to calibrate the readings and finds out that there is more charge than the previous calculations.
This could explain why you see those spikes because the measurement cannot be very accurate all the time : http://batteryuniversity.com/learn/article/calculating_the_battery_runtime
