IMHO kratom in very unique and common rules don't apply here, such as more is usually less with kratom, and less is more, the opposite of regular stuff.
Also the strong extracts are almost always inferior to the plain leaf, which is also odd. The overall strongest (but not necessarl best) results come from mixing extracts with plain leaf, as the extracts are often not working alone. Its just as some people's brain is not able to recognize some alkaloids alone but when they are with other alkaloids they all work.
Anyone interested in kratom should start from plain leaf, forget about getting the strong stuff, or having fun the first time, etc. Kratom is not easy, but if you give it time and respect it can be awesome.