It is syrup:

I translate it for U Frens:

Collected Tilia pour 2 liters of water over the inflorescence, add 3 tablespoons of lemon juice and let it infuse for 24 hours.

Then strain with the cloth, and pour 2kg
of sugar (better is dark from melasa).

Cooking until boil, then 90 minutes.
Beware, it has tendency to overflow.😁

Let calm a while, then bottled.
Now you have healthy 100% natural syrup

Same way you could did with honey...
You put honey onto water, then slowly melt it until have liquid, then put those strained Tilia liquid (without lemon) and calm down honey again...