The ornamental design for a mat for standing, as shown and described.
FIG. 1 is a perspective view of a mat for standing showing our new design;
FIG. 2 is a rear elevational view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof. The broken line shown immediately adjacent to the outermost solid line depicts the interior boundary of the design; with the broken lines and the area within them forming no part of the claim.
The shading and stippled lines in FIGS. 1-6 indicate contour.