I can’t believe this took me an entire day to understand, but there are basically no dictionaries and explanations readily available online in English for the following topic. I tried my best to read through the Japanese websites and explanations I found, but it was getting confusing really fast. I finally understand after asking some Japanese friends on Hello Talk…
For those of you who know, 台 is given multiple different meanings based on context. But before today I had never seen it used combined with “time”and“number” kanji such as 時、分、秒、番、位…
When put together, a counter plus 台 indicates a range or series, starting with the given number and going up to the next “whole”. For instance, 午前10時台 (じだい) means “the range of 10am to 10:59am” and 2万位台 (2まんいだい) means “the range of ranks from 20,000 to 29,999”
While this might not seem useful, I’ve seen this formula come up a lot in sport related topics and in schedule related topics.
For instance I saw this today: 「7秒台後半」 (ななびょうだいこうはん) in a headline in order to describe a baseball batter’s timing from the moment he hit the ball to the moment he touched base, which was 7.77 seconds. (「7秒台後半」 literally meaning “the second half of the 7 second range”, which based on what I said above, we know is from 7.50-7.99 seconds.)
The other way this is useful is with describing time… instead of saying something like 「9時から10時の間」 (9じから10じのあいだ・Between the hours of 9 and 10 o’clock), you can just say 「9時台」 (9じだい) and bam 
you’ve now said the same thing with only two kanji! Essentially the English equivalent of “b/w 9 and 10”
Hope all of that makes sense, and you now have a detailed explanation of this obscure topic that doesn’t seem to be covered by any English resource 