This is the 14943rd most frequent Russian word.
подкреплённые
"Подкреплённые" means "reinforced" or "supported."
Here, "подкреплены" refers to the action of being supported or justified by evidence or facts.
Его слова были подкреплены фактами.
His words were supported by facts.
In this sentence, "подкреплённый" is used as an adjective modifying "доклад", indicating that the report is provided with additional reinforcing data—specifically statistics.
Доклад подкреплённый статистическими данными произвёл большое впечатление.
The report supported by statistical data made a strong impression.
Here, "подкреплены" indicates that the arguments are enhanced or reinforced with real-life examples.