Scoring System

[Sauf]

IIRC Marseille claimed his 17 over 3 sorties in one day, from wiki,

Leaving his fiancée in Rome, Marseille returned to combat duties on 23 August. 1 September 1942 was Marseille's most successful day, destroying 17 enemy aircraft, and September would see him score 54 kills, his most productive month.[47] The 17 enemy aircraft shot down included eight in 10 minutes, as a result of this feat he was presented with a type 82 Volkswagen Kübelwagen by an Italian Regia Aeronautica squadron, on which his Italian comrades had painted "Otto" (Italian language: Otto = eight).[48] This was the most aircraft from Western Allied air forces shot down by a single pilot in one day.

and

Marseille was credited with 17 kills in three separate sorties over El Taqua, Alam Halfa and Deir el Raghat.
His adversaries on the early morning missions were Mk II Hurricanes (No. 1 Squadron SAAF and No. 238 Squadron RAF) and Mk V Spitfires (No. 92 Squadron RAF). One South African, Lieutenant Bailey, was injured in a crash landing, while Major P. R. C. Metelerkamp managed to fly his heavily damaged fighter back to his base. Flying Officer I. W. (Ian) Matthews of 238 Sqn was killed.[118] Pilot Officer Bradley-Smith (92 Sqn) bailed out of his burning Spitfire VC BR474. Bradley-Smith was uninjured.
Among Marseille’s adversaries during the midday combat were Mk IIB Tomahawks of No. 5 Squadron SAAF and Mk I Kittyhawks of No. 2 Squadron SAAF, to which was attached pilots of the 57th Fighter Group USAAF.[Notes 10] Lieutenant Stearns was wounded in the crash-landing of his P-40, Lieutenant Morrison (Kittyhawk I, ET575) remains missing in action, Lieutenant W. L. O. Moon bailed out of his Kittyhawk I, EV366 and was uninjured. Lieutenant G. B. Jack also remains missing in action.
Marseille's evening opponents were Hurricanes from No. 213 Squadron RAF, of which Marseille claimed five shot down.[120] Marseille's 117th official victory was over a Hurricane Mk IIB, BN273. The pilot, Sergeant A. Garrod, bailed out uninjured.