Question

What does 11% and 63% actually mean when we study the phase diagram for a two component system made up of phenol and water?

Answer 1

Starting at the point a, equivalent to a system containing 100% water (pure water) at 50oC, the addition of known increments of phenol to a fixed weight of water, the whole being maintained at 50oC, will result in the formation of a single liquid phase until the point b is reached, at which a minute amount of a second phase appears.
As we prepare mixtures containing increasing quantities of phenol, that is, as we proceed across the diagram from point b to point c, we form systems in which the amount of the phenol-rich phase continually increases. At the same time, the amount of the water-rich phases decreases. Once the total concentration of phenol exceeds 63%, at 50oC, a single phenol-rich liquid phase is formed. The maximum temperature at which the two-phase region exists is termed the critical temperature.

http://physicalpharmacy1424.blogspot.com/2013/06/practical-2-phase-diagram-mutual.html

Answer 2

In few words I can said that beloww 11% of phenol in the mix or above 63% of phenol you will see only one phase at 50C. Between these two values 11-63% you will be able to see a two phase system.