Try to click the “>” after the thick Walnut call out and read what the settings are. If the power is high and the speed under 300 then all you need do is cut the speed by 50 and try it in something small, even some scrap. What @deirdrebeth said about checking is the way to go. As the 
wood has masking on both sides there is some protection against flashback but if there is too much another layer on the bottom is not going to make it harder. to cut
When in doubt it does not take much wood to do this…
and you can start making a reference collection of tests. that will tell you what works