The Probing Level option on the Integer Pre-Solver tab can be used on mixed integer linear programs to perform an operation known as probing. Probing involves taking a close look at the integer variables in a model and deducing tighter variable bounds and righthand side values. In many cases, probing can tighten an integer model sufficiently to speed overall solution times. In other cases, however, probing may not be able to do much tightening, and the overall solution time will increase due to the extra time spent probing.

Pulling down the selection list for the Probing Level field:

you will see that you can choose one of eight different probing levels. A probing level of 1 means probing is disabled, while levels 2 through 7 indicate successively higher degrees of probing. The default setting for this option, Solver Decides, leaves the decision up to LINGO to select the probing level.