MINUS: If you have plenty of shims already there, you can select this option to minimize the number of shims used, since the correction will be accomplished by removing (subtracting) shims.
PLUS: if you have no shims between the motor flange and support flange, to begin with, you can select this option to affect the correction by only adding shims.
PLUS-MINUS: With this option, exactly half of your corrections will be positive (adding shims) and half will be negative (removing shims). This option is very handy if your pump impeller hangs from the thrust bearing in the motor and you do not want to change the pump shaft’s axial position. The plus-minus option makes your pivot point the shaft centerline itself so that the correction will have no z-axis effect on the shaft from shimming at all. This also minimizes the absolute amount of shimming needed.
ZERO-PLUS: This option means all positive shimming but forces one bolt location to be zero (no correction). This is very handy when the bolt circle diameter is the same as the flange diameter, or you already have some shims between the flanges to start with and want to minimize the amount of shimming needed.
ZERO-MINUS: This solution is similar to ZERO-PLUS but in the negative direction, meaning all corrections call for removing shims, with one bolt position at zero correction. This is handy if you have lots of shims already between the flanges and want to reduce these while minimizing the corrections needed.