Excel - shift secondary chart axis to get round values on it

Note: Question starts with a long description, maybe you want to skip. Roll down until you see big heading The real question.

I have table with measured values. There is one set of the values, but two sets of relevant data one is absolute value (time) t and other is relative value (time) Δt showing change from measurement beginning.

I want to show the values with two axis one shows t and other Δt.

So I created scatter chart with two data series.

And made combined scatter & scatter chart from them. Notice different scope of each horizontal (X) axis.

Because I want only one data series shown in the chart I edited X-axis scopes (0-70 for Δt and 7-77 for t). This made both series same (same size and same origin - Value = f(t) is not visible, because is hidden under Value = f(Δt)).

The real question

Now the chart plot a area looks OK. But I'd like to have "nice" round values shown on t axis. It's even possible and if yes, how?

I want the lower x-axis looking like in an image below (ancient mspaint-fu used here :) ).

Solution 1:

Maybe you could add another Helper series, that the X-values include the number that you need on X-axis, the Y-values are all 0.

Then add the series into the chart.

Set no laber for the lower X-axis, but add the lables for Helper series.

Then double click each labe, enter "=" in formula bar, then click the number that you want to show.