It’s “reported twice” because the first time (line 36) it’s part of taxable student income, and the second time (line 43d) it’s subtracted from student income. Taxable scholarships are not considered by FAFSA when computing the FAFSA EFC, and the entry on line 43d is how that money gets removed from the FAFSA EFC calculation.
Is the error message just an advisory thing, or does its appearance prevent you from entering 15,492 on line 43d and then continuing?