I am not sure if i understand your problem correct but try to give you and answer based on my understanding.
I you want to change the range for the x-axis you need (also in MS Excel) to change the range and you cannot do this in the window (X-axis) you opened, You must expand you x-axis data range beyond cell A10 to cover the entire range you want to see in the chart.
Right click on the chart
select data range
select data series
select categories and expand the range here. You can keep the new cells empty or continue from 10 to where you want to go.
LO Calc works correct. The mathematical logic in LO is correct.
If my answer does not help you, could you please explain why you want to do what?
ROSt