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Explanation: mm is originally a term from the oil industry for "millions" and I seem to remember that the reason tey used "mm" instead of the usual "m", is that they wanted to make a differentiation between unit and money.
Your context however seems to show that the abbreviation is being used both with a currency abbreviation and without. In that combination it would seem that the "€ 10,8 mm" is money and the "2,5 mm" is millions of shares.
The URL below gives more than 600 sites using this abbreviation, but I have not been able to find one that gices a conclusive answer.