diff --git a/modules/spl-meter/spl-capture.swift b/modules/spl-meter/spl-capture.swift
index 7c20c87..25a76dc 100644
--- a/modules/spl-meter/spl-capture.swift
+++ b/modules/spl-meter/spl-capture.swift
@@ -253,7 +253,11 @@ let bandN1 = 207                                      // ≈ 20 kHz
 let bandCentres: [Double] = (bandN0...bandN1).map { 1000 * pow(2, Double($0) / 48) }
 
 /// FFT bin ranges per band, clamped to what the transform can actually
-/// resolve. Below roughly 200 Hz a 1/48-octave band is narrower than one
+/// resolve.
+///
+/// This is the one caveat a reader of the RTA needs and the gear is not
+/// allowed to carry (module rule 5, no explanatory text in a tile's
+/// settings): below roughly 200 Hz a 1/48-octave band is narrower than one
 /// bin, so neighbouring bands start sharing bins and the low end reads
 /// smoother than it really is. That is the window length talking, not the
 /// room. Folding to 1/6 or 1/3 puts it right, and a multi-resolution