In this note, we extend the matrix-multiplication analysis by OpenAI to rectangular products and prove $ω(1,k,1)\le2$ for $0\le k\le\frac{1}{2}$, and $ω(1,k,1)\le1+k+\frac{1}{4k}$ for $k\ge\frac{1}{2}$. In particular, $ω(1, \frac{1}{2},1)=2$ and the dual exponent satisfies $α\ge\frac{1}{2}$. The proof uses explicit degenerations of convolution tensors, multinomial counting, and Strassen's spectral theorem. An angular constraint on three dot-product parameters gives both the rectangular curve and a bound for $ω(a,b,c)$. As an application, Zwick's algorithm for all-pairs shortest paths in directed unweighted graphs runs in $O(n^{2.5})$ time. Combining the rectangular bound with the $(\min,+)$-product improvement of Alman and Vassilevska Williams further gives $O(n^{2.4999})$ running time.

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