Clarify caveat comment

src/charts/jBars.js

@@ -159,12 +159,12 @@ export async function jBars (from, to, res) {
         } 
     }
 
-    // noData should be set only if no samples in interval and earlier.
+    // noData should be set only if no bars are in the requested period and earlier.
     // In our case, we are guaranteed to have contiguous samples.
-    // So we only return zero bars if:
+    // So we only return no bars (bars.length==0) if:
-    // 1. interval is before first data available.
+    // 1. period is entirely before first data available.
-    // 2. interval is after last data available.
+    // 2. period is entirely after last data available.
-    // Returning no samples based on length works assuming that TV never asks for case 2.
+    // Returning noData based on bars.length works perfectly assuming that TV never asks for case 2.
     // This is probably not a safe assumption. The alternative would be to search
     // backward to find beginning of history. How far to search?