You can print the early layers (usually support section) faster than the remaining layers, by having thicker z-axis layers.<br>
For example if you are printing in 25 micron and you specify the first 100 layers as low quality, instead of printing 100 layers with 25micron, only 50 layers with 50micron will be printed and it could make the printing process faster.<br>
And this process would not have any effect during the burn-in layers printing.
