i use KC868-E16T for testing, but KC868-E16S is same. connect water level sensor with analog input1.
because the water level sensor output signal is dc 0-5v. level range is 0--70cm
CHA1 and CHA2 use for 0-5v. CHA3 and CHA4 use for 4-20mA
i use pump later water full of bottle.
the big bottle concave about 2-3 cm.
when the water level is 46cm. i test with software and multi meter as follows:
when i change water level from 0-46cm, webpage will auto update the value. i think you need to confirm whether you have use analog 0-5v port?
later i will take a video tour about water level testing.