The Increment option value should be an integer. As explained in
primaryComponent(Ideal,Ideal) the algorithm, given in Eisenbud-Huneke-Vasconcelos, Invent. Math. 110 (1992) 207-235, relies on
topComponents(I + P^m) for
m sufficiently large. The algoritm begins with
m = 1, and increases m by the value of the
Incrementoption until
m is sufficiently large. The default value is 1.