All Maxim data sheet Electrical Characteristics Tables specify:
1. TYP values in the middle column, this is the average value at room temperature
2. MAX / MIN values: these are the worst-case values that will be seen over the operating temperature range (-40°C to +125°C). They incorporate: temperature variation, process variation, with a 6 Sigma spread.
Maxim guarantees that every chip sold will have the parameters in the range between MIN and MAX. MAX14915 250mOhm (max)/120mOhm (typ) ratio is pretty normal, and can be seen on high-side switches from other companies like Infineon and ST. Since the MAX is a 6 sigma value, it is would only be seen with a chance of less than one in a million.