diff --git a/devtimer.py b/devtimer.py
index 53fe809..3596795 100755
--- a/devtimer.py
+++ b/devtimer.py
@@ -1,4 +1,5 @@
 #!/usr/bin/env python3
+
 # devtimer.py - Temperature Controlled Photographic Darkroom Timer
 # Targeted for RaspberryPi
 # Copyright (c) 2018 TundraWare Inc.
@@ -85,6 +86,14 @@
 
 # Program entry point
 
+'''
+  Notice that the actual updating of the display gets run on its own
+  thread.  That's because - on a Pi Zero, at least - it takes over
+  250ms to do this.  We don't want that time added to our timing loop,
+  so we send it off on a parallel thread, and initiate timing for
+  the next round in this thread.
+'''
+
 if __name__ == "__main__":
 
     display0 = TM1637(CLK, DIO, BRIGHTNESS)
diff --git a/tm1637.py b/tm1637.py
index bbadd76..dec9ba6 100644
--- a/tm1637.py
+++ b/tm1637.py
@@ -1,5 +1,5 @@
 # Tip of the hat to https://github.com/johnlr/raspberrypi-tm1637 for
-# this code.  This has been very slightly modified, but it mostly his
+# this code.  This has been very slightly modified, but is mostly his
 # work.
 
 from time import sleep