Hi @jbone,
Welcome, and let me go through your post a little bit…
No problem, we all started with zero knowledge. 
Then we either experiment (and make mistakes) or ask questions to extend our knowledge.
For charging Li-ion batteries, this is almost always the correct setting.
Indeed, a low charging current can extend the lifetime of the battery, but keeping the charge below 100% (for example between 30 and 80%) has a much higher impact. For the current, a good estimate is “0.5C”, which can be roughly translated into “half the capacity value”. So a 3000mAh battery could be charged with 1500mA. Many people prefer to keep it a little lower, though.
The charger can only tell you what charge it has added. You batteries were not completely empty, thus the charger couldn’t add “100%” and reported a lower value. To get a good measurement, you’ll need a charger with capacity test function that measures the capacity during discharge.
Now it becomes dangerous! Li-ion batteries are very sensitive for over-charging. It will drastically reduce the lifetime of the batteries and can even lead to fire and explosion. Charging them once to this voltage will probably not be a safety problem (they have some tolerance above their max allowed voltage), but certainly it already cost you some lifetime.
You might ask, why the charger has this mode? Because there are some special batteries (very rare) with a higher target voltage.
Yes, you are! And you also risk starting a fire.
What’s also important to keep in mind while handling Li-ion batteries? Never short them, never carry or store them without protection. A quick short circuit will immediately cause sparks and very high temperature, possibly welding the wire to the battery terminals where it then stay until the battery explodes.
Also never discharge them below 2.5V. At that voltage a chemical reaction will start which can cause all kind of trouble, often nothing, but often enough it will lead to an explosion. Not while it gets discharged, but when it gets charged afterwards – or even hours or days after charging. So you find a battery with let’s say 1.8V, you charge it to 4.2V, it doesn’t heat up. You put it away. Two hours later it bursts into flames. Yes, that’s when Li-ion batteries are dangerous.
Now discharge your batteries to a safe level (4.2V) and never use that 4.35V setting again with these batteries. And have fun with whatever you use them for.
