Specific color conversion bug

[somnus-L]

`
//pink r 255,g 191, b 204
//crimson r 219, g 20, b 60
//magenta r 255, g 0, b 255
// blue r 0 g 0 b 255

h, s, _ := colorsys.Rgb2Hsv(r, g, b)
s = s * 1000
fmt.Printf("rgbl(%v,%v,%v) => hsv(%x,%x)", r, g, b, uint(h), uint(s))
`
result:
"rgbl(255,191,204,50) => hsv(fffffffffffffff4,fa)"
"rgbl(219,20,60,50) => hsv(fffffffffffffff4,38c)"
"rgbl(255,0,255,50) => hsv(ffffffffffffffc4,3e8)"
"rgbl(0,0,255,50) => hsv(f0,3e8)"

Why do the above three colors appear like "fffff...." after conversion ?