Sarang is a midday measure and a large section, with the later Gurus well represented and a var. It belongs to the group of rags whose performance is traditionally fixed to a particular hour.
That fixing sits in an unresolved relation with the volume's arrangement, which orders by measure rather than by time, and a reading that moves through the Granth in sequence will not be observing the hours. Practice accommodates this rather than resolving it, and the accommodation differs between lineages of musicians.
What is settled is what the page requires: this composition, in this measure. What is not settled is whether the surrounding culture's conventions about when a measure is sung apply to scriptural material, and the volume does not address the question.
The section itself is among the more substantial in the second half, which is worth noting because the second half of the Granth is often described as a run of shorter sections. That description holds for a stretch of it and not for the whole. Sarang, Bhairo, Maru and Ramkali are all large, and the tail of the volume is not a diminuendo so much as an alternation, with the very short sections and the very long ones interleaved in an order the volume does not explain.