I will start from afar to explain in slightly more details about という expression. It's not completely alien for English speakers, but it's a bit tricky, because usually we don't pay much attention to it.
In any language there are more concrete items and more general concepts about what it represents. For example, word flowers in "Take care of these flowers" represent something factual, very specific in front of our eyes. But flowers in "One of the most expensive spices are flowers called Saffron" represent the kind. The reason why it's even used here is because speaker isn't completely sure that all listeners would understand what Saffron is, especially when people were talking about spices to begin with. So we mention the kind, what generally it is, and more specific unit on which we want to focus. There are many similar situations when we want to talk more abstract ideas, what something represent. For example, when we say "the fact that X happened means...", we want to shift from factual occurrence to more abstract idea that such thing can mean generally. For example, "The fact that she remembers your birthday or your preferences means that she's paying attention to you (she likes you or she cares about you)".
In Japanese という is essential for it. It can be used in several slightly distinctive situations:
- Xと言った "(Someone) said X"
- 姫という酒場 "Bar called Princess"
- サフランという花 "Flowers called Saffron"
- 自分の娘と会わないということは考えられない "I can't imagine not seeing my daughter"
It's not inclusive, there might be other usages, but it has a gradient to show the idea. In the first example いう is used directly, so there are no nuances. But in the second example people have a small problem. If we say "Let's go to the bar", then it might be not obvious which exactly bar we mean. Similarly if people aren't aware about such bar, then "Let's go to the Princess" doesn't even make any sense. We need some tool to combine both, specific name and what it represents and such tool in Japanese is という. Third example is very similar to it, but in my opinion it has slightly different flavor. While giving names for places, books, movies and other things can be informative, sometimes people want to explain something or give their interpretation of it. Similarly we can try to find out such explanation or confirmation, if such thing exist and it's what we think. Very often it's used in pair with こと, so we get ということ for different kinds of explanations and interpretations. I decided to mention the forth example, because it's the peak. It's so abstract that it exist only theoretically, person can't believe that such thing is even possible and it's always going to be used with という.
ということでしょう from your example is very simple, because it's purely №3. Person tries to explain what it is and gives his own interpretation. But I'm not sure about 3秒という時間. It might be similar to №2, but it's different. In 姫という酒場 we can't change it, something like 姫の酒場 would produce completely different meaning, but 3秒の時間 is possible. There are many different wordings too, we can use 3秒間 or 3秒間の, so there should be a reason why person wants to use という variation. My guess is that sometimes people use という by feeling, the idea of という is that we can think about some broader unit being split on different categories. When we say 姫という酒場, we understand that there are many different 酒場 and we want to focus on one of these. Therefore if people feel that it's not simply a time of some activity, but a category instead, they would tend to use という for it. For example, if we are talking about breathing techniques, then holding your breath for 3 seconds could be a variation of it. But it's purely my speculation and can be completely wrong.