FT index issue

We have a web application which is having following error on teh server console: GRT Search error…Full Text message: Work area overflown due to many hits. Error-Number = 299

There is not much about this issue on the internet which would be

related to 8.5.2 server.

Application if quite big, about 4GB and has about 321000 documents.

There are no documents bigger than 10MB.

Our server is running 8.5.2FP1.