I am assuming you are referring to the "maximum" input parameter that we pass as part of *-list-info-iter-next APIs.
You can pass any valid integer (as per API Documentation). And yes, you can specify 10000.
If the number of objects/records are less than the value of "maximum" input parameter provided by you, then all the objects/records will be returned in the same response.
In other words, you can indeed use a large number like 10000 to get all records in same response instead of iterating several times.
However, be aware of the fact that if there are lots (close to 10000) of records and each record contains large amount of data (the XML output structure), then the single response construction (at server side) and XML parsing (on client) may take a huge amount time and also in some cases may timeout. In such cases, it may be more efficient to iterate over the records in smaller chunks (i.e. multiple responses with smaller value of "maximum" input parameter).