The catalogue does not identify a separate base return. RTP Ledger leaves the base return unknown. Use the mode table for the published values.
At the two-decimal display precision, 12 modes share the highest displayed RTP of 96.7%: 4x4 m5 s3 boost v6ext, 4x4 m5 s3 boost v6med, and 5x5 m10 s3 super v6ext and 9 more. 16 modes share the lowest displayed RTP of 96.2%: 5x5 m12 s2 base v6ext, 5x5 m12 s2 base v6med, and 5x5 m13 s2 shield v6ext and 13 more. The difference between the displayed extremes is 0.5 percentage points.