Hi Frank,
Greetings from Syncfusion. We would like to let you know that, in the stacked series, when there are multiple series all the series will be stacked one over the other, and this is the behavior of stacking series. If you wish to move the 64 value of the second series below the first series, we suggest using the normal line series and not using the stacked line series. This will help you to achieve your scenario.
Thanks,
Yuvaraj