As seen from the above chart, in the primary layer of compensation, ship owner takes insurance for the liability  as per CLC 92. 

For ships upto 5000GRT, liability is 4.51 Million SDR and for every ton above 5000GRT it is 4.51 Million SDR+ 631 ( GRT-5000). 

In the Supplemenatry layer of compensation, the contributions are made by the Oil receivers ( Oil companies). 

Now in order to ease the burden on these oil companies who are contributing to the IOPC fund and also to show the ship owners commiment  in sharing the burden with the oil companies ( which in a way will give more buisness to the Ship owners) and also to increase the minimum liability from 4.51 Million SDR, owners of small tankers have have entered into  a voluntary agreement with the P& I clubs to increase the minimum liability from 4.51 Million SDR to 20 Million SDR. This will also benefit  the IOPOC and Supplementary Fund, as there will be no need to revise the limits of liability. 

Hence the figure 29548 GRT. 

4.51 Million SDR + 631 x (29548-5000)= 20 Million SDR approx. 

So under the terms of STOPIA, the liability of the owners of small tankers upto 29548 GRT is increased  to 20 Million SDR. 

TOPIA 2006 is another form of independant agreement which provides indemnification to the Supplementary Fund for 50 % of the amounts ( claims) paid by the Fund. 

As of today there has been only 2 incidents involving vessels entering in STOPIA 2006 and no incidents of vessels with TOPIA 2006 as there has been no incident which involved the use of Supplementary funds.