A developer, without violating the terms of the approval pursuant to this subsection, may, in undertaking any section of the planned development, reduce the number of residential units or amounts of nonresidential floor space by no more than 15% or reduce the residential density or nonresidential floor area ratio by no more than 15%; provided, however, the developer may not reduce the number of residential units to be provided pursuant to the Township's fair share plan approved by the council on affordable housing, without prior municipal approval.