My train starts at six, arriving in Chicago at ten.

1. My train starts at six, arriving in Chicago at ten.
2. He entered college at the age of eighteen, graduating four years later at the head of his class.

Source: An Advanced English Grammar, Bao Bing, The Commercial Press, China

These are two sample sentences from the book above, but I don’t think they are correct. Here is my reason.
When the present participle is used as adverbial, the action of it happens at the same time as that of the main verb. But in the first sentence, the time gap is four hours and in the second sentence, the time gap is four years.
I’d like to read your comment.

I think the sentences are fine, but I would say "departs” instead of "starts”, and "top" instead of "head".
That is the "duration", not "time gap". "Time gap" is to do with a lapse of an activity.

I don’t quite understand how “starting/departing” could last for four hours and how “entering” could last for four years.

They can't. All three actions are punctual - that have no duration.

diamondcutter said:

When the present participle is used as adverbial, the action of it happens at the same time as that of the main verb.

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Not necessarily.

Louis fled to Aix in 1812, dying there six years later.

Do you think the two sentences in the OP are correct?

@diamondcutter
1. Rather than "starts" I would say "departs" (or "leaves").
2. More natural would be "at the top of his class" or "in the top half" or something like that.

diamondcutter said:

I don’t quite understand how “starting/departing” could last for four hours and how “entering” could last for four years.

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That wasn't what I meant. The activities continued for the durations. Departing and arriving are non-continuous actions of course.
What is the relevance of "time gap"?

tedmc said:

That wasn't what I meant. The activities continued for the durations.

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No activities are mentioned.

5jj said:

No activities are mentioned.

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The activities of the train travelling and the student studying in college.

Those activities are not mentioned, ted.

They are understood. The activities or course of the activities lasted the durations stated.

When we are talking about tense, aspect, duration, punctuality, etc, we consider the information we have, not what we can infer. In "My train starts at six, arriving in Chicago at ten", the duration of the journey is irrelevant to the grammar.

Many English grammar books in China say that when the present participle is used as adverbial, the action of it happens at the same time as that of the main verb or the two actions have at least a common time point, for example, the ending point of the first action is the starting point of the second. Now I know this so-called rule is not true. Dear learners, is there a similar rule in the English grammar books in your countries?

diamondcutter said:

Dear learners, is there a similar rule in the English grammar books in your countries?

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That question would be better asked here:

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