In the documentation at https://www.django-rest-framework.org/api-guide/throttling/ the allowed throttling periods are indicated as second, minute, hour or day .

Further in the same page, an example shows, instead, the use of just min.

Looking at the source code it is evident that just the first letter of the period is considered:

I think this should be clarified to the user, e.g. something like:

The throttling period is specified after the / separator by using s, m, h or d . The use of an extended unit such as second, minute, hour or day or even sec, min, hr is allowed too (only the first character is relevant).