I have recently discovered that my master cylinder when filled to the fill mark will drop to above min and then hold at that level. There are no leaks on the system and it won't drop any further throughout use.

The brake pedal is nice and firm and works fine.

Am I just worrying over nothing or is something serious causing the problem?

Do you keep repeatedly have to fill it or was it once only? After a brake pad change perhaps?

It's s sealed system so if you have to fill it up more than once it's leaking somewhere.

Last time it was filled was when I bled the clutch system at xmas which was roughly 12months after a pad/discs and a full system bleed for fresh fluid. I recall it being similar levels at xmas time also which is now why I'm thinking an issue maybe present.

My thoughts was if it was a leak, wouldn't the level be dropping further and further instead of holding in the 'acceptable range' on the fluid tank?