Exemption to Small Scale Service Provider

Dear All, Please help

For current F.Y, Central Govt. has exempted Taxable Service of aggregate value not exceeding 10 Lacs from the whole of service Tax .

Provided, the aggregate value of Taxable Services rendered during the preceding F.Y doesn't exceed Rs. 10 Lacs.

Now my query is as to "while computing Rs. 10 lacs limits for Preceding F.Y, what do we have to consider,whether amount of Service Tax billed or amount of Service Tax received during the Previous F.Y ? "