Numbers Chart Date Axis Set Minimum and Maximum

It's a two-step process.

First off, you will need to work out the number of steps. In my quick testing, Numbers like to make 4 steps on the X axis, regardless of the time span. You'll need to work out the number of months in the timespan and manually set that in the Major Steps field in the Inspector:

Then, assuming you have dates in your X axis, Numbers is probably showing full dates that don't align (something like '1/2/25 10:00', which isn't helpful, so in the Inspector, you can define how the labels should be shown.

Finally, if you want to show the month boundaries on the chart, check the gridline settings:

and you should get something like:

I see now... you're right.

I got closer with my graph settings:

but still not what you want. The issue is clearly that it's dividing the time period into 7 equal periods, which don't match to the first of the month (thanks February!).

I was able to get even closer by adding a series of Custom Reference Lines, one per month:

But that's a lot of work and doesn't scale well.

I did run the table through Excel for comparison, and Excel's ability to use dates for the axis units certainly simplifies this.

So that may be your option at this point. Might be worth dropping a line to Feedback - Numbers - Apple

(referencing this discussion) and hope for a future update.

January to July is 7 months. You have your Major Steps set to 6. Try setting it to 7.