At 350°F, the maximum shrink is achieved. You won't use this setting very often, but it's important to know the total shrink temperature range. That's because the amount of shrink rate you'll have left is based on the temperature you use to shrink the covering.
For example, if you're shrinking your film using 320°, by referring to the chart, you'll find that 82% of the total remaining shrink is left. That's good! That means that, if in the future you need to re-shrink the covering, it won't be a problem. But a word of caution: use the highest temperatures only as a last resort to shrink wrinkles and imperfections. In most cases, if you need to use this much heat, you'd be better off to just replace the covering with a new piece.
Watch out for...
Stay away from seams and edges. This high temperature can cause bubbling and blistering.