| Schedule of information on dividends of convertible preferred stock | 
  
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  | 
  | 
August 31, 2022  | 
  | 
May 31, 2022  | 
 
(in thousands)  | 
      | 
Series B  | 
      | 
Series C  | 
      | 
Series D  | 
      | 
Series B  | 
      | 
Series C  | 
      | 
Series D  | 
 
Shares of preferred stock  | 
  | 
  | 
 19  | 
  | 
  | 
 6  | 
  | 
  | 
 9  | 
  | 
  | 
 19  | 
  | 
  | 
 7  | 
  | 
  | 
 9  | 
 
Total shares of common stock if converted  | 
  | 
  | 
 190  | 
  | 
  | 
 12,670  | 
  | 
  | 
 10,565  | 
  | 
  | 
 190  | 
  | 
  | 
 13,806  | 
  | 
  | 
 10,565  | 
 
Undeclared dividends  | 
  | 
$  | 
 11  | 
  | 
$  | 
 -  | 
  | 
$  | 
 -  | 
  | 
$  | 
 10  | 
  | 
$  | 
 -  | 
  | 
$  | 
 -  | 
 
Accrued dividends  | 
  | 
$  | 
 -  | 
  | 
$  | 
 2,186  | 
  | 
$  | 
 2,175  | 
  | 
$  | 
 -  | 
  | 
$  | 
 2,014  | 
  | 
$  | 
 1,963  | 
 
Total shares of common stock if dividends converted  | 
  | 
  | 
 22  | 
  | 
  | 
 4,372  | 
  | 
  | 
 4,350  | 
  | 
  | 
 20  | 
  | 
  | 
 4,028  | 
  | 
  | 
 3,926  | 
 
 
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| Schedule of outstanding balances of convertible notes | 
  
For additional information about the Company’s debt policies, refer to Note 2, Summary of Significant Accounting Policies, of the 2022 Form 10-K. Outstanding balances associated with the Company’s convertible notes and related accrued interest are as follows:  | 
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  | 
  | 
August 31, 2022  | 
  | 
May 31, 2022  | 
 
(in thousands)  | 
      | 
April 2, 2021 Note  | 
      | 
April 23, 2021 Note  | 
      | 
Total  | 
      | 
April 2, 2021 Note  | 
      | 
April 23, 2021 Note  | 
      | 
Total  | 
 
Convertible notes payable outstanding principal  | 
  | 
$  | 
 9,819  | 
  | 
$  | 
 28,500  | 
  | 
$  | 
 38,319  | 
  | 
$  | 
 9,819  | 
  | 
$  | 
 28,500  | 
  | 
$  | 
 38,319  | 
 
Less: Unamortized debt discount and issuance costs  | 
  | 
  | 
 (359)  | 
  | 
  | 
 (1,127)  | 
  | 
  | 
 (1,486)  | 
  | 
  | 
 (512)  | 
  | 
  | 
 (1,566)  | 
  | 
  | 
 (2,078)  | 
 
Convertible notes payable, net  | 
  | 
  | 
 9,460  | 
  | 
  | 
 27,373  | 
  | 
  | 
 36,833  | 
  | 
  | 
 9,307  | 
  | 
  | 
 26,934  | 
  | 
  | 
 36,241  | 
 
Accrued interest on convertible notes  | 
  | 
  | 
 2,920  | 
  | 
  | 
 4,200  | 
  | 
  | 
 7,120  | 
  | 
  | 
 2,599  | 
  | 
  | 
 3,375  | 
  | 
  | 
 5,974  | 
 
Outstanding convertible notes payable, net and accrued interest  | 
  | 
$  | 
 12,380  | 
  | 
$  | 
 31,573  | 
  | 
$  | 
 43,953  | 
  | 
$  | 
 11,906  | 
  | 
$  | 
 30,309  | 
  | 
$  | 
 42,215  | 
 
 
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| Schedule of changes to outstanding balance of convertible notes | 
  
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
 
(in thousands)  | 
  | 
April 2, 2021 Note  | 
  | 
April 23, 2021 Note  | 
  | 
Total  | 
 
Outstanding balance at May 31, 2022  | 
  | 
$  | 
 11,906  | 
  | 
$  | 
 30,309  | 
  | 
$  | 
 42,215  | 
 
Amortization of issuance discount and costs  | 
  | 
  | 
 153  | 
  | 
  | 
 439  | 
  | 
  | 
 592  | 
 
Interest expense  | 
  | 
  | 
 321  | 
  | 
  | 
 825  | 
  | 
  | 
 1,146  | 
 
Outstanding balance at August 31, 2022  | 
  | 
$  | 
 12,380  | 
  | 
$  | 
 31,573  | 
  | 
$  | 
 43,953  | 
 
 
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