Bubble Chart - Multiple Series

Hello - if anyone could assist that would be greatly appreciated.

I cannot seem to add additional series into a Bubble Chart. the second series bubbles seem to overwrite, or extend the X-axis values.

I have attached a sample. I have added a comment beside the two rows that I cannot seem to add without screwing-up the chart.

Do I need to set the data set-up in a different format?

I seem to have read somewhere that others had this problem.

Thanking you in advance?