How much/fast is a battery allowed to degrade?
The battery is doing well.
Lithium Ion (LiIon) &amp; Lithium Polymer (LiPo) batteries are essentially identical for practical purposes.
LiIon/ LiPo batteries have cycle lives typically in the 300-600 cycles range for relatively deep discharge use, and you can get substantially more cycles of lower discharge depth. As discharge depth decreases the maximum total energy stored and retrieved increases. eg a battery that gave 500 x 100% discharge cycles or 500 x initial capacity but the same battery may give 1200 x 50% discharge cycles or 600 x initial capacity.

As well as cycle life LiIon batteries have a "calendar life" - 'the clock starts ticking' as soon as they start to get used and a battery with minimal use will still have a finite lifetime. 

In the example here there have been 610 cycles in about 700 days - we do not know how long from manufacture to start of use - so maybe only 600 days of use or approaching one cycle per day. This suggests that the user charges the battery every day regardless of state of charge at end of the day. It is also possible that your friend charges the battery at work (university, school ...) and at home   so gets 2 cycles per day. And they may have it on power most of the time so that the discharge depth is seldom very high.

I do not know how Apple measure "cycles" - they might determine % of charge to full and call that say 60% or 30% of a cycle but it is much more likely that they call every charge a cycle.  

So - it is not possible to know from the information provided how much use the battery has really had, but the figure given is well within the range of normal".