Can you please explain me the equation (2) at page 9? I do...

Dear Emanuele,
thank you for your question. Equation (2) was introduced in case anyone would need to use different volumes of any reagent, due to for instance high or low concentrations of glycogen in the cells, or high or low amount of cells in the samples. In such cases, the protocol can be easily followed, only the amount of reagents is adjusted.

I belive our intention here is well described in the paragraph preceding Equation (2):

In case of using lower or higher volumes of algae/cyanobacteria suspension than 1 ml (Step A1) and/or in case of diluting the samples by lower or higher volumes of distilled water than 500 μl (Step C2) or 300 μl (Step D17), and/or in case of adding lower or higher volumes of 5% phenol than 500 μl (Steps C5 and D20), calculate the final carbohydrates concentration according to the equation (2).

Best regards,
Tomas