From what I see, the errata for the Seeker is as follows:
1. for Supplement 7, the two ore bays are 9 tons each, not 10 tons.
Since it's all payload, when interpreting the specified modifications I typically lose two of the staterooms, 10 dtons of fuel that would otherwise support Jump, and then shave the 3 dton cargo hold to 1 dton (since the original cargo hold isn't explicitly mentioned in the Seeker write-up); thus preserving the 2 x 10 dtons ore bay capacity.
Also, for the fussiest of SPA inspectors (and borrowing from HG2), you can even fit 100 dtons worth of L-Hyd drop tank supports (do not waste money and displacement on buying the actual tanks); then you can defensibly claim that your operating fuel profile (J plus PP) meets Imperial safety regulations despite being technically 10 dtons short when you do not have L-Hyd mounted (which, frankly, will be most of the time anyway).