f clarify that the base penalties are cumulative

Author: TheBlueMatt

lightning/src/routing/scoring.rs

@@ -331,7 +331,8 @@ pub struct ProbabilisticScoringParameters {
 	/// Default value: 500 msat
 	pub base_penalty_msat: u64,
 
-	/// A fixed penalty in msats to apply to each channel, multiplied by the payment amount.
+	/// A fixed penalty in msats to apply to each channel, multiplied by the payment amount, in
+	/// excess of the [`base_penalty_msat`].
 	///
 	/// The purpose of the amount penalty is to avoid having fees dominate the channel cost (i.e.,
 	/// fees plus penalty) for large payments. The penalty is computed as the product of this
@@ -340,6 +341,8 @@ pub struct ProbabilisticScoringParameters {
 	/// ie `amount_penalty_multiplier_msat * amount_msat / 2^30`
 	///
 	/// Default value: 8,192 msat
+	///
+	/// [`base_penalty_msat`]: Self::base_penalty_msat
 	pub base_penalty_amount_multiplier_msat: u64,
 
 	/// A multiplier used in conjunction with the negative `log10` of the channel's success