Construction D₀ Radio Button is Disabled for Log(time) Curves

§12.5.1.2 of ASTM D2435-11 places several constraints on the t/4t construction:

• The dial reading at 4t should be greater than the initial dial reading plus 25% of the total displacement for the increment.
• The dial reading at 4t should be less than the initial dial reading plus 50% of the total displacement for the increment.

In some cases it's impossible to select a t/4t interval that meets both of the above criteria. When it encounter such a case the program disables the "D₀ by construction" option.