On June 30, 2020, the Company issued 1,718 shares of common stock, in aggregate, for debt conversions of $1,000 aggregate principal amount of the 8% Notes, related shares of Series C Preferred Stock, and of $4,185 aggregate principal amount of the 10% Note. The Company also issued 93 shares of common stock for Series C Preferred Stock discussed above (Note 10).

Restricted Stock

The Company did not grant restricted stock during the six-month periods ended March 31, 2021 and 2020. Stock-based compensation expense attributable to restricted stock was $163 and $336, and $130 and $885 during the three and six-month periods ended March 31, 2021 and 2020, respectively. As of March 31, 2021, there was approximately $482 of unrecognized compensation expense related to restricted stock outstanding with vesting period 3 years.

A summary of restricted stock activity is presented as follows:

No warrants were granted or exercised during the six-month periods ended March 31, 2021 and 2020.

Stock Options

As of March 31, 2021, there were stock options outstanding under the Company’s Amended and Restated 2013 Incentive Stock Plan. During fiscal 2020, 2013 Incentive Stock Plan was amended to increase available balance by 1,000 stock options. Compensation Committee of the Board of Directors authorized to grant either incentive or non-statutory stock options to employees. Vesting periods are established by the Compensation Committee at the time of grant. All stock options outstanding as of March 31, 2021 and September 30, 2020 were non-statutory stock options, had exercise prices equal to the market price on the date of grant, and had expiration dates ten years from the date of grant.

Stock-based compensation expense attributable to stock options and warrants was $130 and $268, $226 and $68 for the three and six-month periods ended March 31, 2021 and 2020, respectively. As of March 31, 2021, there was approximately $400 of unrecognized compensation expense related to unvested stock options outstanding, and the weighted average vesting period for those options was 3.95 years.