| In millions, except per share items | May-31-23 | May-31-22 | May-31-21 | May-31-20 | May-31-19 | May-31-18 | May-31-17 | May-31-16 |
| | 10-K | 10-K | 10-K | 10-K/A | 10-K | 10-K | 10-K | 10-K |
| Net sales | 5.3 | 18.9 | 7.2 | 6.7 | 5.2 | 5.6 | 5.8 | 5.1 |
| Net sales growth | -71.7% | 162.1% | 7.6% | 28.7% | -6.5% | -3.9% | 12.7% | 3.6% |
| Cost of sales | -4.9 | -15.9 | -6.8 | -5.0 | -3.9 | -3.8 | -3.8 | -3.6 |
| Gross profit | 0.4 | 3.0 | 0.4 | 1.7 | 1.3 | 1.8 | 2.0 | 1.5 |
| Gross margin | 8.4% | 15.8% | 5.1% | 26.0% | 24.8% | 31.5% | 34.9% | 29.7% |
| |
| Operating expenses: | | | | | | | | |
| Selling, general and administrative | 6.1 | 5.7 | 5.7 | 2.5 | 2.0 | 1.8 | 1.8 | 1.6 |
| Research and development | 1.6 | 1.8 | 2.2 | 1.9 | 1.7 | 1.4 | 1.1 | 0.8 |
| Total operating expense | 7.7 | 7.5 | 7.9 | 4.5 | 3.7 | 3.2 | 3.0 | 2.4 |
| Loss from operations | -7.2 | -4.5 | -7.5 | -2.7 | -2.4 | -1.5 | -1.0 | -0.8 |
| Operating margin | -135.3% | -24.0% | -104.2% | -41.0% | -46.4% | -26.6% | -16.5% | -16.1% |
| |
| Other income: | | | | | | | | |
| Dividend and interest income | 0.1 | 0.0 | 0.1 | 0.1 | 0.0 | 0.0 | 0.0 | 0.0 |
| Other income | 0.0 | | | | | | | |
| Total other income | 0.1 | 0.0 | 0.1 | 0.1 | 0.0 | 0.0 | 0.0 | 0.0 |
| Loss before income taxes | -7.1 | -4.5 | -7.4 | -2.7 | | | | |
| Provision for income taxes | -0.1 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | | -0.7 |
| Net loss | -7.1 | -4.5 | -7.4 | -2.7 | -2.4 | -1.5 | -0.9 | -1.5 |
| |
| Basic net loss per common share | ($0.50) | ($0.36) | ($0.62) | ($0.26) | ($0.26) | ($0.17) | ($0.11) | ($0.20) |
| Diluted net loss per common share | ($0.50) | ($0.36) | ($0.62) | ($0.26) | ($0.26) | ($0.17) | ($0.11) | ($0.20) |
| |
| Weighted average number of common and | | | | | | | | |
| Basic | 14.2 | 12.7 | 11.9 | 10.2 | 9.2 | 8.6 | 8.3 | 7.6 |
| Diluted | 14.2 | 12.7 | 11.9 | 10.2 | 9.2 | 8.6 | 8.3 | 7.6 |
| |
| Other comprehensive loss, net of tax: | | | | | | | | |
| Foreign currency translation | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Comprehensive loss | -7.2 | -4.6 | -7.5 | -2.7 | -2.4 | -1.5 | -0.9 | -1.5 |