If you fence the first day, take your overall seed (X*P) and subtract 16. This is your seed into the pools the first day, call it S. There will be 200*P-16 fencers in the pools, so (200*P-16)/7 pools, always rounding up. Call it N pools. If your seed S is smaller than or equal to the number of pools N, then you are (on paper) the strongest guy in the pool. If N > S but N <= 2*S, then you are the second strongest. If N > 2*N but N <= 3*S, then you are the third. Etc.
You can estimate what the strength of the fencers will be in your pool, given your world ranking and the attendance at the tournament.
First figure out which pool you are in. If your first day seed S is greater than double the number of pools N (i.e., S > 2*N) subtract 2*N from S before doing this part. Keep subtracting 2*N until you get a number less than 2*N. (This would be mathematically phrased "S modulo 2*N"). If S <= N, you are in pool S. If S > N, then you are in pool 2*N-S+1.
So you are in pool M. The people in pool M will be the fencers with the first day seeds M, 2*N+1-M, M+2*N, 4*N+1-M, M+4*N, 6*N+1-M, and maybe M+6*N if it's a pool of 7.
From those first day seeds, you can calculate back to what their world ranking is. Take their first day seed S, add 16 for the byes to the second day, and then divide by the attendance P. Thus, their world ranking X=(S+16)/P.
In practice this gets you a rough idea of what the strength of the fencers in your pool will be, but doesn't predict who will actually be in it.
You need to figure out how you will do against those fencers: How Will I Do In My Pool?