Hydrogen Bond in MD

GROMACS version:
GROMACS modification: Yes/No
Here post your question Hello
I ran a molecular dynamics simulation and anlayzed the number of Hydrogen bonds, which showed fluctuations between 0 to 6. what does that mean?

Not to state the obvious, but it means there are between 0 and 6 hydrogen bonds in each frame between your selected groups.

thank you so much for your reply
I understand but why is that happening,

In general, because things move during an MD simulation, so interactions may break and form over time.