What is it meant by gold changes in this sentence?

Question

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Time spent in making gold changes during the coal loading sequence.

Answer 1

The phrase "in making gold" is a prepositional phrase, which means that you can omit it and the sentence is still a sentence.

Therefore the sentence reads, (without the prep. phrase)
"Time spent changes during the coal loading sequence"

I think it means that there is a variable here-the time varies with the different coal loading sequences. Different coals mean different times/different loadings means different times.

Just an educated guess. Hope this helps.