Add a comment on timestamp scan

src/scales/scale.time.js

@@ -341,9 +341,13 @@ function computeOffsets(table, ts, min, max, options) {
 	var i, ilen, timestamp, length, upper, lower, divisor;
 
 	if (options.offset) {
+		// First, it processes `ts.labels` to pick up timestamps of labels, which are
+		// primarily used for offset calculation because bars are usually on labels.
+		// But if there are no labels, it should add offsets based on `ts.data` because
+		// we support bars with {t, y} data points as well. That is the second path.
 		[ts.labels, ts.data].forEach(function(data) {
 			if (!timestamps.length) {
-				// Remove labels outside the min/max range
+				// Remove timestamps outside the min/max range
 				for (i = 0, ilen = data.length; i < ilen; ++i) {
 					timestamp = data[i];
 					if (timestamp >= min && timestamp <= max) {