Remember to read the manual!
Read the manual here
Volts: Volts is a measure of electrical force. I like to think about it as how hard the electricity is "pushing". When your batteries have low voltage, they don't have enough force to make your appliances work and as a result lights will dim and fans will turn slow down. All you need to understand about Volts right now is that 100% on your batteries is approximately 13.6-13.8V and that your batteries will cut themselves off around 10.5V. The battery voltage is in the bottom left of the screen.
Amps: Amps (short for Amperage) is the flow of electricity. The higher the amps, the more electricity is flowing at once. Amps are located to the right of the voltage at the bottom left of the screen. In the context of understanding your battery monitor, the amps here represent the net flow of power to or from your battery bank. If you have a negative sign (-) by the amps, that means that the power being consumed is greater than the incoming power from charge sources (solar or shore power). Since the power being consumed is greater than the incoming, the batteries must discharge in order to supply the loads with the power that they need. If you have a positive number it means the opposite, that the incoming power is greater than the power being consumed. That means that the extra power is used to charge the bttteries.
I like to think of it as being similar to a checking account. If you have $1,000 in your bank account and every month you spend $200 and make $100, you have spent more than you have taken in and you have netted -$100. It is possible to do this with your ROAMER 1 trailer. It is possible to consume power faster than you are bringing it in.
Amp-hours: Amp hours is a common measure of battery capacity along with Watt hours. Both are similar. The name pretty much explains most of it. a 100Amp-hour battery can expend 1 amp for 100 hours or 100amps for 1 hour. The math isn't exactly so simple, but the concept is the same. On a base level, this value represents the same inforamtion as the percentage.
Watts: Watts is a measurement of power. It is made up of Volts x Amps, it means watts charging or watts discharging. It tells you the rate at which you are charging or discharging depending on the sign next to the amps. If the sign next to the amp flow is negative, then the watts value represents the watts that are being drawn from the batteries. If the sign is positive, the watts represent the watts that are being put to charge the battery.