diff --git a/README.md b/README.md
index 5aaec0b..ea18911 100644
--- a/README.md
+++ b/README.md
@@ -69,8 +69,9 @@ should be calibrated manually after setup as each sensor is different:
 1. Turn on the Supersensor in a known-clean environment (e.g. a sealed clean
    container in fresh air).
 2. Leave the sensor on for 4-6 hours to burn in.
-3. Record the maximum Gas Resistance value (in Ω) and round up to the nearest
-   5,000-10,000 or so (e.g. 96,938 => 100,000).
+3. Look at the historical graphs for the Gas Resistance sensor and find the
+   maximum value over the burn-in period.
+4. Round the maximum Gas Resistance value **up** to the nearest 1000.
 4. Divide the rounded maximum Gas Resistance value by 1000 to get the kΩ value.
 
 This value will then define what "100% air quality" represents, and the
diff --git a/supersensor.yaml b/supersensor.yaml
index c9fbe55..e4787bf 100644
--- a/supersensor.yaml
+++ b/supersensor.yaml
@@ -514,6 +514,7 @@ sensor:
     name: "BME680 AQ"
     id: bme680_aq
     icon: "mdi:gauge"
+    unit_of_measurement: %
     # Calculation from https://github.com/thstielow/raspi-bme680-iaq
     lambda: |-
       float ph_slope = 0.03;