By limiting to only 100 MB in your case your getting a lower speed because your connection is taking a long time to build up.
TestMy.net Test ID : nNvoumYgN TestMy.net Test ID : Kcx-bIyPH
The speed in the second graph, where you selected auto size, starts out faster because during the first initial loads of the test (as it determines the right size) is warming up the connection. So by the time the final test starts, which is what your actual result is calculated from, you've already probably downloaded over 100MB. So then that result is higher... because the connection has warmed up past where the real issue is. (your issue is in how your speed starts... looks like that connection finishes really strong)
This is why I'll always have the option to select your own size manually, I think it's a super important option for troubleshooting. To my knowledge TMN is the only internet speed test that offers manual test size options.
