Considering acceleration of $10~m/s^2$ at launch. To calculate the $\delta V$ lost at launch pad.
$$\delta V = 10 \times \delta t$$ where $\delta t$ is time taken by SRBs to break the stud.
I think $\delta t$ can be around 1 second, though I cannot find source to get correct number. If that assumption is correct
$$\delta V = 10~m/s$$ therefore,
Considering total time to orbit as $500~s$ $$\delta S = 10 \times 500 = 5~km$$
Is this a severe trajectory impact? What kind of margins can STS tolerate on trajectory or underperformance and still operate?