Grove A12-200 current sensor
You are measuring a sinusoidal "signal" that is alternating in polarity. What the code notes as "effective" current the equivalent DC current for purposes of measuring power consumption. In EE, it's called "RMS" or Root Mean Square, and it's the mathematical derivation to calculate consumed power or current in a situation where the current flows symmetrically back and forth, and thus a time average would give zero.

It's dividing the peak current by the square-root of 2 (1.414).