Because the Finnish victories are checked against Soviet loss records.
The link your gave is confirmed victories from Finish side to their own pilots, not by soviet archives.
http://www.warbirdforum.com/scores.htm
For instance on spetember 1941, the 17th, the 24LLeV was harshly opposed to 14 MiG-3 of the 179 IAP. Finish pilots claimed (and obtained) 7 victories, in fact neither side suffering losses.
17.09.41 LeLv 24 Alho, M.A. BW-383 1.00 MiG-3 Okay / in fact NOK=0
17.09.41 LeLv 24 Dahl, J. BW-393 1.00 MiG-3 Okay/ 0
17.09.41 LeLv 24 Ikonen, S.H. BW-386 1.00 MiG-3 Okay/ 0
17.09.41 LeLv 24 Korhonen, A. BW-387 1.00 MiG-3 Okay/ 0
17.09.41 LeLv 24 Torronen, I.V.S. BW-385 2.00 MiG-3 Okay/0
I don't know who claimed the last MiG.
So high 6 - 7/0 overclaim = infinite
Some Finish claims (confirmed or not) are validated by soviet archives, some are clearly invalidated (no losses at all that day, that place), some are with unknown (not verified on russian archives yet) or uncertain status (might by shooted by fighters, might not..)
Regards