Problems - partially solved - using Gemma (v2) with Arduino IDE 1.6.4

I have had several stumbles during the path to getting my new Gemma 2 (from Adafruit) to work, though I have managed to work out most of the wrinkles and have been able to download and run successfully a version of the ubiquitous "Blink":

/*
  Gemma_Blink
  
  Turns on an LED on for one second, then off for one second, repeatedly. Note
  that since the user-accessible LED is connected to I/O pin 1 (instead of pin 13
  on the Arduino Uno), this sketch toggles pin 1.

  Modified May 27 2015
*/

#define LED 1               //user-accessible LED is on I/O pin 1

void setup() {
  pinMode(LED, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(LED, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);              // wait for a second (1000 milliseconds)
  digitalWrite(LED, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);              // wait for a second (1000 milliseconds)
}

What worked for me was to follow Adafruit's instructions for adding boards to the Arduino v1.6.4+ IDE:

Then by trial and error (after reading other user's results), I selected "USBtinyISP" in Tools>Programmer. I can select either "Arduino Gemma" or "Adafruit Gemma 8MHz" in Tools>Board and am able to download code.

The only problem I'm having - and am treating as merely a nuisance at the moment - is that after programming, the IDE gives this error message:

avrdude: error: usbtiny_receive: (expected 4, got -5)

Since my very simple code is up and running, I'm not bothered too much (at this time) - but I would like to understand what is going on. Any clues? I'll be looking into this a bit more, but am interested to hear what others have experienced with the Gemma. For what it's worth, my computer is running Windows 7 Home Premium; I have not tried other computers.