This step should specify removing the film from strip 15, such that repeating the step again for strip 14 in the next step isn’t confusing. Or this step could specify both strip 14 and 15 and step 19 could be deleted entirely.
The trick with removing the left speaker is that you have to slide it up toward the top of the iMac (continuing to de-route the power button cable carefully as you go) to get it out from under the chin before you lift it up to remove it.