Grid Target is defined by two main parameters applied separately to each Lab coordinates separately

Step

Step defines change applied to the neighbor patch. Depending on the direction it will be increased or decreased. Small step ( about 1.0 might produce a slight difference when the number is higher 2-4  differences are stronger. Any values higher produce dramatic variations, but the user may set even very high values. Take into account that big steps may very fast exceed the printing device gamut.

Range

The user may select a number of samples. The smallest value is +/-1 = what means we have 3 patches (-1, 0, +1). If the +/-6 range is selected 13 patches will be generated.  Take into account that page size will affect patch width and corresponding font size. Small media size (Letter) should rather be used with the smaller range as a single patch size matters for visual judgment.

Roundtrip ΔE_ab (gamut warning)

This is a definition of the threshold for gamut warnings. There are two important scenarios where gamut warning is critical.

Some samples can be inside the printing device gamut, however where we create variations (especially with big steps or/and using a higher range). We should be warned that based on information calculated by Color Management engine we know that some variants are out of the supported color space. If it happens - we should try to reduce steps and/or range or try to use another printing device that offers a bigger gamut.

If we are limited to 8-bit color space - limitations coming from that may produce values that are addressed inaccurate. You may expect that value 0.7 or even higher can point some patches as out of the gamut - and only the reason is that roundtrip ΔE_ab calculation exceeds the limit.