When you open as ASCII file and choose Ncurves for Element Type, this dialog box appears.
Least Squares Optimize
Check the box to use this optimization method.
Check Points Per Span
The Knots of a NURB spline divide the spline into a number of spans. Each span will be evaluated at the number of points specified by this parameter. One or more arcs may result from this evaluation.
Optimize Deviation
This is the maximum allowable chordal deviation of the spline from the lines drawn between the chosen points.