The grantedMaxFrequency is defined as "an upper limit on the frequency that may be imposed as a limitation in some specific editions of the product".
In the product page we refer to it as the "Max Message Rate (Downstream)".
Admittedly, the definition is a little dated, as the value is not strictly related to the edition, but, for Enterprise edition, it is an optional feature of a specific contract and it also depends on the kind of license. However, it can be chosen only among the values 1, 3, and unlimited.