What is the white spot on this egg

[Imammusa]

My hen just lay this egg with this white spot that can be scratched off if I use my something. What do you think it is?

 

[CluckerFamily]

If it can come off, I believe it is calcium build up.

 

[aart]

Agrees, excess calcium.

'Speckled' eggs can happen for several different reasons...very few, if any, of which are a 'problem'.
Can be caused by:
Excess or uneven pigment coating.
Excess or uneven cuticle(bloom).
Excess calcium deposits.
Porous eggs can appear speckled.
Some birds lay them consistently, some only once in awhile.
The pigment or bloom can change appearance when wet, then change back when dry again.

As long as bird is getting a good diet and is healthy in every other way, it is no cause for concern.