Working Voltage for Basic/Reinforced Isolation (ACS712)
You'd need to read UL standard 60950-1, 1st Edition as cited in that exact table! Google can give you that document, you're looking for clause 1.2.9.2 to 1.2.9.5. 

Basically, to cite the above document scientifically:


  1.2.9.2 BASIC INSULATION : insulation to provide basic protection against electric shock
  
  1.2.9.3 SUPPLEMENTARY INSULATION : independent insulation applied in addition to BASIC INSULATION in order to reduce the risk of
  electric shock in the event of a failure of the BASIC INSULATION
  
  1.2.9.4 DOUBLE INSULATION : insulation comprising both BASIC INSULATION and SUPPLEMENTARY INSULATION
  
  1.2.9.5 REINFORCED INSULATION : single insulation system that provides a degree of protection against electric shock equivalent to
  DOUBLE INSULATION under the conditions specified in this standard


Meaning that for the lower voltage range, this chip might be used and the isolation can be labeled as "reinforced", whereas it's only basic if used in the higher voltage range. 

In other words, the thing is designed so that you can think it being "as secure as say a cable with isolation, plus another isolating measure in case that isolation fails". This makes a difference in applications where you need the double isolation-equivalence. I can't tell you whether that is required for your application – chances are you want to put all this in a foolproof and safe enclosure, so that it's not overly critical if everything inside fails and the measurement side of the chip accidentally sees 230V.

Also, 230V might indicate that UL standards don't matter to you, at all.