Jesus!

From his Wiki page

Some of Häyhä’s figures are from a Finnish Army document, counted from the beginning of the war, 30 November 1939:

22 December 1939: 138 sniper kills in 22 days[21]
26 January 1940: 199 sniper kills (61 in 35 days)[22]
17 February 1940: 219 sniper kills (20 in 22 days)[7]
7 March 1940 (one day after he was wounded): total of 259 sniper kills (40 in 18 days)[7]

Häyhä never discussed it publicly, but his own private memoir, discovered in 2017, states a number. He begins by stating that “this is his sin list”, and estimates the total number he shot to be around 500.

Probably the source of this joke

The Soviet army is marching through a Finnish forest when a general hears a voice from over a hill shout: “one Finnish soldier is better than 10 Soviet soldiers!”

The general promptly send 10 soldiers to root out the voice, there is gunfire, and then silence.

After a few minutes, the voice shouts defiantly: “One Finnish soldier is better than a hundred Soviet soldiers!!”

The general sends a hundred men to remove the nuisance, there is a racket of gunfire, and then quiet.

The voice cries out loudly once more: “One Finnish soldier is better than a thousand Soviet soldiers!!”

Enraged, the general sends a thousand men charging over the hilltop to shut up that voice once and for all, an epic battle rages, and then quiet. After a few minutes, a gravely wounded Soviet crawls back over the hill and cries:

“It’s a trap! There are two of them!”