A supplier report can contain many measurements. Start with the result you are trying to understand: hardness, taste and odour, particles, or a safety parameter.
Find the supply zone
Reports normally relate to a defined supply zone or sampling area. Confirm that the report covers your address and note the date and sampling period.
Understand hardness units
Hardness may be shown as mg/L or ppm as calcium carbonate, or in degrees such as German, French or Clark degrees. Do not compare numbers until you know the unit. Use the hardness checker for conversions.
Read results in context
An average is useful for orientation but does not describe every property or every day. Sudden changes in colour, smell or taste should be raised with the water supplier rather than solved by guessing at equipment.
For background, read the UK water-hardness guide and the drinking-water section.