Anchor Tenant wants sole access to showers

We’ve got a core and shell commercial office building in construction, under 300,000 square feet, using CS-2009. The project is primarily office, with some retail and restaurant at the ground level, and we’ve been tracking this credit. Based on our total FTE, we calculated a need for 3 showers/changing rooms; the design incorporated 4 (2M+2F). However, a tenant has now signed a lease for more than 90% of the total office space, and they want sole access to those 4 showers/changing rooms. We understand that the showers should be available for anyone in the building to use, but if we assume these 4 showers are available to only this anchor tenant, how would we calculate the remaining needed showers? Should we just provide for 0.5% of the remaining 10% of tenants? If the result is less than 1, is it acceptable to provide 0 additional showers? Or should we just round up to 1 (unisex)?