These are my corrections to finalize your writing. Please, meet my notes and deal with them.
Overall, the viewer watching at 6pm news decreased slightly while 1pm visitor remained stable. August experienced a top for 11 pm while for 9.30pm news, it jumped to the lowest point.
Actually, you have written the overview well, but you have to know what you write. Pay attention to the meaning. There were changes in the quantity, not the viewer.
OVERALL, THE NUMBER OF VIEWERS WATCHING NEWS AT 6PM HAD DECREASED SLIGHTLY, WHILE THE PERCENTAGE AT 1PM HAD REMAINED STABLE. AUGUST EXPERIENCED A TOP FOR THE RATE OF THE VIEWERS AT 11 PM, BUT FOR 9.30PM, ITS RATING JUMPED TO THE LOWEST POINT.
..., it can be seen that the PROPORTION FOR viewers OF
news ON CHANNEL ONE fluctuated and (...) below 5 MILLION to just below 3.5 MILLION PEOPLE. although THE PROGRAM OF 11pm news was first (...) just above 4 million
AS the most highest (...) to just above 1 MILLION
REPRESENTING the smallest number of it.
... December, THE PROGRAM OF 9.30pm news was (...) increase to 3 MILLION.