diff --git a/experiments/dsv4_h200_vllm_tp_dp_matrix/config.env b/experiments/dsv4_h200_vllm_tp_dp_matrix/config.env
index 1652629..61b8be2 100644
--- a/experiments/dsv4_h200_vllm_tp_dp_matrix/config.env
+++ b/experiments/dsv4_h200_vllm_tp_dp_matrix/config.env
@@ -30,9 +30,10 @@ declare -a PARALLEL_CONFIGS=(
 MATRIX_FILE="${MATRIX_FILE:-${SCRIPT_DIR:-.}/matrix.json}"
 MATRIX_MODE="${MATRIX_MODE:-Y}"
 
-# Sampling density for concurrency. 0 means use the default heuristic in
-# generate_scenarios.py (6-8 points, or all integers when range is small).
-CONCURRENCY_SAMPLES="${CONCURRENCY_SAMPLES:-0}"
+# Sampling density for concurrency.
+# 0  = use the default heuristic in generate_scenarios.py (6-8 points).
+# 2  = only test the two endpoints (low and high).
+export CONCURRENCY_SAMPLES="${CONCURRENCY_SAMPLES:-2}"
 
 # Per-scenario timeout to avoid hangs (seconds).
 SCENARIO_TIMEOUT_S="${SCENARIO_TIMEOUT_S:-1800}"