The fragment is a bicyclic system formed by fusing a pyrrolidine to a 1,2,4-triazine ring. Use the following numbering:

- The 1,2,4-triazine ring is a five-membered aromatic ring with three nitrogens in a 1,2,4 distribution; number it N1-N2-C3-N4-C5, with C5 and N1 fused to the pyrrolidine.

- The pyrrolidine is a saturated ring with a single nitrogen. This single nitrogen ring is shared in the fused ring system; number it C5(shared)-N1(shared)-C6-C7-C8, closing back to C5.

Substituents and stereochemistry
  - At C3 (on the 1,2,4-triazine ring): there is a chiral carbon (S-configured) that connects to C3, to a fluorine, and to a cyclopropyl group (a saturated three-carbon ring); the fourth substituent is hydrogen.
  - At C6 (on the pyrrolidine): C6 is S-configured and bears a benzene ring.
  - At C8 (on the pyrrolidine): C8 is S-configured and bears a fluorine.