The information Ampere provides can vary depending on whether you're connected to a power source, but generally it can tell you the status of the battery, current battery percentage, technology used in its manufacture, temperature, model, device version, and IP address. If your device is charging, the application can also tell you the voltage coming from the power source to which you are connected.
After a pre-scan, you can see the amp-hours your device is receiving when it's connected and how much it's consuming without it. With this data, you can calculate the mA you need to charge your battery at a normal rate.
When the device is not connected, you'll see the value as a negative number. To charge it, you need a difference of at least 200 mA. So, for example, if your device consumes 300 mA, you'll need a charger that gives you at least 500mA if you want to use the device as it charges. The less energy you have, the less efficient the charging method.