I don't know where they got those figures from but according to the Stockholm International Peace Research Institute the Russia is the second biggest arms dealer with sales over the last ten years of 72514 million, Germany second with 19923 million, then France 18876 million, then China 15709 and Britain in with place with 12990 million. 2018 is the latest year for which figures are available. Britain was in eighth place with 740 million in sales compare to Russia's second place 6409 million.
Just go here and you can get figures for the period you choose. http://armstrade.sipri.org/armstrade/page/toplist.php
You do not mention which country was the biggest arms dealer. Was it the country which supplies us with our nuclear weapons?
By this reckoning Britain emerges with little credit for restraint.
In fact, the enlightened western countries are no better than Russia and China.
We have a government department pushing arms sales.
"If we did not sell the stuff, then someone else would" is the self justification of the drug dealer.