"[If] the organization's Section 833(c)(5) MLR computed on an aggregate basis is at least 85 percent, the organization will satisfy the Section 833(c)(5) MLR for the taxable year. If the organization's Section 833(c)(5) MLR computed on an aggregate basis is not at least 85 percent, the organization will not satisfy the Section 833(c)(5) MLR for the taxable year.... [T]he Section 2718 medical loss ratio is computed by market segment, but the Section 833(c)(5) MLR is computed on an aggregate basis. As a result, it is possible for an organization to be required to issue Section 2718 medical loss ratio rebates to enrollees by market segment for a reporting year, but on an aggregate basis satisfy the Section 833(c)(5) MLR for that taxable year.... [W]hether for a given taxable year an organization can include rebates issued to enrollees under Section 2718(b) with respect to a prior reporting year as an expense in computing its Section 833(c)(5) MLR depends on the HHS guidance in effect for that year."