diff --git a/svc/product_series_auto_scheduler.go b/svc/product_series_auto_scheduler.go
index cd44224..e888fce 100644
--- a/svc/product_series_auto_scheduler.go
+++ b/svc/product_series_auto_scheduler.go
@@ -695,13 +695,19 @@ ORDER BY d.id, r.priority DESC, r.id
 	}
 	out := make([]productSeriesAutoRule, 0, len(byID))
 	for _, r := range byID {
-		if len(r.Ratio) == 0 {
-			for _, part := range strings.Split(r.Title, "-") {
-				size := normalizeProductSeriesSize(part)
-				if size != "" {
-					r.Ratio[size] = 1
-				}
+		// Always augment ratio map from the dfgrp.title tokens.
+		// mk_product_series_rule can be partially populated (or manually edited), which would allow
+		// a "subset" rule (e.g. only M+XL) to match stock and incorrectly assign a series like
+		// "XS-S-M-L-XL-2XL". Title tokens are the canonical definition of a series in this setup.
+		for _, part := range strings.Split(r.Title, "-") {
+			size := normalizeProductSeriesSize(part)
+			if size == "" {
+				continue
 			}
+			if _, ok := r.Ratio[size]; ok {
+				continue
+			}
+			r.Ratio[size] = 1
 		}
 		if len(r.Ratio) > 0 {
 			out = append(out, *r)