diff --git a/src/nvfp4_megamoe_kernel/cutlass_nvfp4_gemm/cutlass_nvfp4_gemm.cu b/src/nvfp4_megamoe_kernel/cutlass_nvfp4_gemm/cutlass_nvfp4_gemm.cu
index 5ae26fe5..dc7c25de 100644
--- a/src/nvfp4_megamoe_kernel/cutlass_nvfp4_gemm/cutlass_nvfp4_gemm.cu
+++ b/src/nvfp4_megamoe_kernel/cutlass_nvfp4_gemm/cutlass_nvfp4_gemm.cu
@@ -135,18 +135,18 @@ __global__ void remap_sf_to_cutlass_kernel(
     int mn, k_sf_val, src_idx;
 
     if (col_major_src) {
-        // source is row-major (K_sf, MN), e.g. SFB stored as (K_sf, N)
+        // Source is (K_sf, MN) row-major in memory — e.g. SFB after transpose+contiguous
         k_sf_val = tid / MN;
         mn = tid % MN;
-        src_idx = tid;
+        src_idx = tid;  // tid = k_sf_val * MN + mn
     } else {
-        // source is row-major (MN, K_sf), e.g. SFA stored as (M, K_sf)
+        // Source is (MN, K_sf) row-major — e.g. SFA
         mn = tid / K_sf;
         k_sf_val = tid % K_sf;
-        src_idx = tid;
+        src_idx = tid;  // tid = mn * K_sf + k_sf_val
     }
 
-    // Use layout forward mapping: source (mn, k_sf*16) -> dst_idx
+    // Use layout forward mapping: (mn, k_sf*16) -> dst_idx
     constexpr int LayoutRank = cute::rank_v<decltype(layout_sf.shape())>;
     int dst_idx = 0;