TOL is a built-in variable which is used to achieve desired accuracy and speed for numerially computed answers in Mathcad.
TOL, which has a default of 0.001, controls the precision to which integrals and derivatives are evaluated. When you set TOL low, all results are computed with much greater precision. This may increase computation time. High values of TOL will decrease computation time at the expense of precision.
Type TOL= to see what the tolerance is set to. It should be greater than 0 and less than or equal to 1.
To reset TOL, just redefine it by typing