Examples:
For Amphibians by quantity and 4 amphibians:
{{By quantity|amphibians|Amphibians|amphibian}}
For 1 turtle, 2 turtles, 3 turtles, and 5 turtles:
{{by quantity|turtles|Turtles|turtle}}

The parameters |prefix= and/or |suffix= may be used for lengthy category titles.

For 1 person in the United States, 2 people in the United States, and so forth:

{{by quantity|people|3=person|suffix=in the United States}}

For Groups of 1 in Hesse, Groups of 2 in Hesse, and so forth:

{{by quantity|prefix=Category:Groups of|suffix=in Hesse}}

This template can also be used for categories that feature numbers but do not designate quantities. In this case, |header= must be used.

For Category:0 icons, 1 icons, and 99 icons:

{{by quantity|icons|Icons|icons|header=[[:Category:Number icons|]]}}

This template currently has no relevant documentation. Any editor familiar with the purpose and usage of this template is requested to write some documentation.