As you just want to disply the e.g. last 30 days you might be better with data filter excluding all but the last 30 rows (or using the date column). This will autoadjust the scaling in Graph Builder and you have just the data you want, independent of the order the data gets into the data table.
If you nest e.g. lot and date, be careful of the order of nesting. Date should then be the most outer one. Otherwise you might remove the wrong rows adjusting the min value for the axis. Why? As with increasing min value it cuts from left to right the data, which means from the most left lot first. This might not reflect the true dates or in other words it probably will cut also dates you want to show and leave in the "old" dates in the more right grouped lots.
A Filter would provide you the option to filter the lots you want to see within a specific time frame. As well you could get the number of rows first and automatically adjust the filter.