Question

A question on thermodynamic and empirical temperature scales..
In a constant volume gas thermometer,the ratio of pressures is used to determine the ratio in temperatures.in the book:

Sears, F.W. and Salinger G.I., “Thermodynamics, Kinetic Theory and Statistical Thermodynamics"

the author states that this pressure is to be taken limiting.what is meaning and use of taking 'limiting' pressure?how can the limit be taken when one of the numerator is a constant and the denominator is a variable?

anyone who knows about this,please help!!