Different languages have different grammatical numbers. For most IE languages, these are Singular, Plural and, sometimes, Dual.
Other languages have grammatical numbers differentiated by the quantity of 'items' (from Dual to Trial, e.g. in Bislama, and Quadral, as in Sursurunga). Many Austronesian languages have paucal number depending on quantity of 'items' counted (up to 27).
Other languages (including samples of extinct Sumerian) have two more types of grammatical number not defined by the quantity of items, namely, Collective (as opposed to Singulative) and Distributive (as in Navajo or in Finnish 'kuukausittain' = 'by [separate groups of] months', 'parvittain' = by [separate quantities of] animal groups, 'kerroittain' = 'by [separate groups of] times [of events]', etc.
Sumerian, according to Kaneva (2006 in Russian only) also had a 'Sortive' type of grammatical number.
In ancient Tocharian languages (at least in Western Tocharian), there had been a Dual and a Pair Grammatical numbers; the former was applyed for random pair combinations, and the latter, for natural and inseparable ones (like 'eyes', 'nostrils', etc.).
In Basque, there is also a type of 'Indeterminate' (literally, 'Infinite') grammatical number ('mugagabea'), or verb aspct.
Are there any other types of grammatical numbers in other languages?