If it is black denim and they say to avoid washing it as much as possible, how should it normally be cared for?

On the surface, these two lines seem to point in opposite directions. One says to avoid washing as much as possible, while the other meticulously sets out the method for when you do wash it. The reason both lines exist together is simple: this garment can lose its color when washed, so to preserve its original black color, it is better to reduce the number of washes altogether^[1][2].

Even so, the day when you must wash it does come. At that time, you must hand-wash this garment alone in cold water, and do not use a dryer^[3]. For drying, machine drying can damage the product and should be avoided, with instructions guiding you to hang it in a ventilated shade to let it dry naturally^[4]. Generally, the more lukewarm or hot the water is, the more dye bleeds out, and the heat of a dryer easily leads to shrinkage or fabric damage.

To the extent washing is reduced, color transfer is what needs attention while wearing it. If worn together with bright-colored clothing or suede materials, the color may transfer^[5], and because that degree can increase on days with sweat or high humidity, special care is needed when wearing it with white clothes^[6]. The outer fabric consists of 66% cotton, 30% polyester, plus rayon and nylon, with soft washing applied^[7][8]; generally, darkly dyed washed denim may rub color off in the early stages of wear, so it is also better to keep an eye on items that come into contact, such as bright bags or sofas. When concerned about odors or wrinkles, hanging it for about a day in a well-ventilated, shaded spot rather than washing, and gently spot-cleaning localized stains right where they occur are commonly used methods.

hmmm, rather than being contradictory guidelines, these two lines are closer to an advisory aimed at preventing that single characteristic—color fading—from both sides: washing and wearing.