You seem to be using TSVB, not Lens. For TSVB you can select an interval for the buckets that are retrieved from Elasticsearch so you can change from the default auto (that in your case is converting into 3 hours) to any valid value.
With Lens the Last value formula does not perform any other aggregation.
In any case both visualizations are always by default constrained by the Kibana time range picker on the top right of the screen. In dashboards you can customize your time range per panel to override the global time range.
On this clip I clone an existing lens visualization (using the new metric type) to pick a very large range, so you see how the same metric can be queried for different time ranges.