So technically they are asking for the area of the glass that will be installed...
by the 3.14 for pi I take that it is a circle-ish shape.
so to find the area we take the area of a circle which is
A = pi r^2
to plug in what we know
A = (3.14) times (2)^2
this is A = 3.14 times 4
A = 12.56
they will need a glass with the area of 12.56 ft^2
Hope this helps ;)