This is limited by design from EV 8 SP1:
http://seer.entsupport.symantec.com/docs/326716.htm
In EV8.0, SP1, the limits for the numbers of Search Result items displayed by Browser search has been changed. [Ref 801455, E1161980]
IIS does not allow uploads of large amounts of data by default. The amount of data that can be uploaded is controlled by the property AspMaxRequestEntityAllowed. In earlier releases of Enterprise Vault, if you tried to add 1,000 items to a basket from one Search Results page, the default limit set by AspMaxRequestEntityAllowed could be exceeded and an error message displayed. It is not advisable to set the default limit too high, so the maximum number of items Browser search displays on one Search Results page has been reduced.
The numbers of items that Browser search displays on one Search Results page are now:
* Normal search: 10, 25 or 50
* Advanced search: 10, 25, 50, 100, 250 or 500