Your battery shows a negative amperage whenever it isn't being charged. When it reaches full charge, charging stops until the battery gradually drains to below 95% of full charge. This is normal and as designed.

Can you have negative amperes?

So, there is no "negative volts" or "negative amps" as such - we use the sign to show, that the voltage or current just is "other way around" compared with the agreed "positive direction."

Can you have a negative current?

Negative current is current flowing in the opposite direction to positive current, just like the axes on a graph have negative and positiva in opposite directions.