He accidentally erased some of the computer's memory, which caused the inertial measurement unit (IMU) to contain data indicating that the module was in the same relative orientation it had been in before lift-off; the IMU then fired the thrusters to "correct" the module's attitude.
hiː ˌæksɪdˈɛntəli ᵻɹˈeɪst sˌʌm ʌvðə kəmpjˈuːɾɚz mˈɛmɚɹi, wˌɪtʃ kˈɔːzd ðɪ ɪnˈɜːʃəl mˈɛʒɚmənt jˈuːnɪt ˌaɪˌɛmjˈuː tə kəntˈeɪn dˈeɪɾə ˈɪndᵻkˌeɪɾɪŋ ðætðə mˈɑːdʒuːl wʌz ɪnðə sˈeɪm ɹˈɛlətˌɪv ˌoːɹiəntˈeɪʃən ɪt hɐdbɪn ɪn bᵻfˌoːɹ lˈɪftˈɔf; ðɪ ˌaɪˌɛmjˈuː ðˈɛn fˈaɪɚd ðə θɹˈʌstɚz tuː "kɚɹˈɛkt" ðə mˈɑːdʒuːlz ˈæɾɪtˌuːd.