[Grammar] Simple Past + a specific time

Hello, everybody!
I found this explanation on the Internet (http://www.englishpage.com/verbpage/pastcontinuous.html):

In the Simple Past, a specific time is used to show when an action began or finished.

Examples:

• Last night at 6 PM, I ate dinner.

Now if I get it right, this sentence can mean either I started eating at 6 PM. or I finished eating at 6 PM.?
How to know when is which?

You can't from that sentence. Normally the time would indicate the beginning of the meal, but 6 PM may be approximate.

I think 'start/finish dinner' indicates the beginning/end of the meal.

It is clear, however, that the meal cannot start and end at 6 PM.

So mostly the meaning (start/finish) rides on the context, right?
I'm really grateful for the answers, it makes it easier

Iryn_ said:

it makes it easier

Click to expand...

See below.

Rover_KE said:

End every sentence with the correct punctuation mark — not home-made emoticons. If you want to insert a smiley, click on the :-D icon.

Click to expand...

Iryn_ said:

Now if I get it right, this sentence can mean either I started eating at 6 PM. or I finished eating at 6 PM.?
How to know when is which?

Click to expand...

As Mike said, it is unlikely to refer to the end of the meal. However, if it really mattered, we would say I started dinner at 6 and finished at 6.20, or something like that. If accuracy is important then we will express ourselves accurately. If it isn't particularly important, then we often don't bother. The person is saying that they had dinner early in the evening rather than late.