DAC offset error vs. output low voltage
The "Output Low Voltage" is listed under the "Digital Interface" section of the datasheet. It is the maximum allowable output voltage when the I2C interface is trying to send a logical zero. It is unrelated to the DAC analog output. Therefore, the "Offset Error" is your minimum output voltage. It also biases every other DAC output level as well.

Check section 4.5 of the datasheet:



From Microchip MCP4725 Datasheet