An inner merge keeps records whose keys match in both queries. The first query is the left table, the second is the right table, and the selected key columns must describe the same thing with compatible types. Power Query adds a nested table column first. Expand it to choose which fields become ordinary columns.
A merge isn't automatically a one-row lookup. If a route has two roster entries, each matching job produces two rows when you expand. That can be correct when both drivers need a dispatch copy. It can also inflate totals when someone expected one driver per route. Know the intended grain before removing duplicates.
Exact text matches are case-sensitive. Spaces, inconsistent case and missing identifiers deserve attention before joining. Null keys can match other null keys in Power Query, but that doesn't prove two unknown routes are the same route. Filter missing keys when the business request requires a known identifier.