How do i clean up a polyurethane stain from a composite deck?

<p class="s570a4-10 iEJDri">Long story short, I moved into a new condo yesterday, had my interior floors screened, and the floor guys left noticeable stains on the shared front porch (composite decking).</p> <p class="s570a4-10 iEJDri">I&#039;ve called the floor guys to clean it up but</p> <p class="s570a4-10 iEJDri">a) they aren&#039;t making it a high priority</p> <p class="s570a4-10 iEJDri">b) I&#039;m worried they&#039;ll do a bad job of cleaning and I&#039;ll have to finish it myself anyway.</p> <p class="s570a4-10 iEJDri">I want to make sure this gets done well since my literal first introduction to my upstairs neighbor was him pointing out the stains (oops). I&#039;d like to make a better first impression than that as a new neighbor:-/</p> <p class="s570a4-10 iEJDri">What&#039;s the best way for me to clean up noticeable poly stains of the deck without doing more damage?</p>