A high number can always be scary.
There’s a good bit of discussion here on the forum and elsewhere about the fact that a calcium score (Agatston CAC score) measures only calcified (i.e., scabbed over, “healed”) arterial plaques - not the soft ones, which are the truly dangerous plaques more prone to being dislodged and cause a clot somewhere else.
The calcified plaque indicates prior damage.
The other limitation of an Agatston CAC score is that it does not properly incorporate the role of plaque density (mass divided by area). The more dense the plaque, the more complete the scabbing and healing underway.
Ultimately, it’s the change over time in one’s CAC score that sheds the most light on what’s happening. Four months on keto would be far too early to tell, even if you had years of base line CAC scores for self-comparison. The scabbing/healing takes much longer than that.
Meanwhile, I might suggest reading up on research relating to Vitamins K2 and D3, which in combination are key to ensuring any excess calcium in circulation is more likely to wind up in bones and teeth. 