Worst case error for a DAC
That article seems fine but you also have to consider temperature effects if not being held constant at one temperature. For instance there will be a gain error temperature coefficient and this might be 20 ppm / degC meaning that if there is a change in temeperature of 30 degC there could be a further error in the gain of 600 ppm (parts per million) or 0.06%.

Same applies to the offset error and you need to ensure that INL is specified to be a max value within the temperature range you are expecting. Don't forget to consider local heating effects on your circuit from (say) linear regulators - they will warm things up a bit more.