No it means that the battery voltage is 12 .45 V, nothing more , nothing less.
Now you have 2 problems
1) the engine is not starting
2) the engine is not charging
There is a small chance that they are connected but usually not.
You are there & we are here you are ours eyes, ears & noses
So you need to be far more specific about what it does when you try to start it, what you see what you hear and what you smell.
Now for the charging.
Start your engine.
Take your Fluke around to the regulator
Check the AC Voltage between the two outside wires which is your AC feed directly from the stator.
At full speed you should see something between 26 and 45 V AC
Next Switch to DC and measure from the center terminal and ground.
You should see better than 12.45 V ( battery voltage ).
If not check the ground strap to the rectifryer.
On Kohler rectifryers the body of the rectifryers is the ground terminal so needs to be grounded to the engine by a strap as it is mounted in the plastic blower housing.
I make up a second wire so both mounting bolts are grounded ( belts & braces ).
If all that is good follow the middle wire, usually purple.
You can not be bothered to tell us what we are dealing with so I have no idea of how it is wired into the mower.
So you now will have to follow this power feed all the way back to the battery looking for the broken link.