Meaning of AT Parameters?

[GWheelerEB]

When running WHAM-BAM, the resulting VCF has an info-field 'AT', which is a comma-separated list of 15 numerical values; however, I cannot find any information as to what these fields actually mean. I know that the classify_WHAM_vcf.py script uses these values to run a ML model and assign an SVTYPE to each variant call, and I was also able to find a note in the documentation saying, "The average user should not worry about this field." Beyond that, there does not appear to be any explanation.

Could you possibly provide a brief explanation as to what these fields correspond to, or is there advanced documentation elsewhere that I missed?