It just means that the input voltage range is 1.4V. The absolute minimum and maximum values depend on the input common-mode voltage about which your circuit is biased.
For example if in a single-ended (or differential) configuration, having a single power supply, if you have a input common mode of say, 0.9V, then, your input signal will swing from 0.9-0.7V to 0.9+0.7V.
If it is mentioned as differential peak-to-peak, your signal will swing from 0.9-0.35V to 0.9+0.35V in one of the differential inputs and would be antiphase in the other differential input.
Hope this helps.