There are differing opinions on this but here is how I see it.
For Gail, the number of biopsies is a surrogate for the presence of Atypical Hyperplasia. Gail assumes that 10% of biopsies show atypical hyperplasia. If the biopsy result is unknown, than give anyone with a biopsy 10% of the risk associated with atypical hyperplasia. As a core that does not lead to an excision is unlikely to have shown atypical hyperplasia, I would tend to not count it as a biopsy at al. This is controversial.
For Tyrer Cuzick, I would say similarly not to count it, but as TC increase risk based on hyperplasia without atypia as well as atypical hyperplasia, the answer is less clear. I would say not to include cores in Gail ever, and to include only cores with atypia for TC.