What does the display of the 4480 wattmeter read when the forward power is less than what the selected range is specified to cover?

While the 4480A low band and high band have minimum specified accuracy at 10 W and 1 W, respectively, power levels that fall below this will still be detected and displayed; the measurement area will not be blanked out, get populated with dashes/hyphens, or read any form of "out of range" message. See images of each band setup below.