Bard 2024-01-25: BCSQ=@1887: This refers to a quality score for the variant call stored at another location in the VCF file (at line 1887). This is mostly correct.

.... it continues: This score is likely calculated using the Bayesian Confidence Score (BCS) method, which takes into account various factors like mapping quality, variant frequency, and strand bias. I don't think this is correct, I think BCS is unrelated.