In the single supplied attestation (Māṇḍūkya mūla 10), svapnasthāna designates the "dream-place" or dream-state, identified with taijasa and correlated with the second mātrā of OM, the syllable u (ukāra). The verse grounds this correlation in u's "exaltation/intermediacy" (utkarṣa) and its sharing of features with the elements on either side (ubhayatva), and promises that one who knows this exalts the continuity of knowledge (jñānasaṃtati), becomes equal/impartial (samāna), and has no non-knower of brahman in his lineage. Beyond this one mūla locus the corpus supplies no further evidence.
Senses
The reading surface. A later ingestion attaches a locus to a settled sense, or proposes a new one (dashed) for human triage — it never rewrites settled prose.
1 · The dream-state/dream-place identified with taijasa, the second of the four quarters, corr…settledadded v1
The dream-state/dream-place identified with taijasa, the second of the four quarters, correlated with the syllable u (ukāra) of OM by reason of its exaltation/intermediacy (utkarṣa) and its sharing in both adjacent elements (ubhayatva).
2 · The dream-state as the locus/abode of the dreamer (svapnasthānavat draṣṭṛ); the dream as a…proposedadded v2
The dream-state as the locus/abode of the dreamer (svapnasthānavat draṣṭṛ); the dream as a place within which the dreamer wanders and perceives objects, and to which the dream-properties (apūrva sthānidharma) belong, distinguished from the OM-syllable/four-quarters correlation.
Śaṅkara (bhāṣya) — Āgamaśāstrabhāṣya on the Māṇḍūkyakārikā
Why a new sense: These attestations treat svapnasthāna concretely as the dream-locale in which the dreamer dwells/moves and perceives, bearing peculiar dream-properties — not the taijasa/ukāra/OM-quarter correlation captured by s1.
v1Māṇḍūkya mūla + Gauḍapāda kārikā — +1 loci 1 sense(s) drafted from 1 loci.
v2Śaṅkara bhāṣya — +5 loci · 2 routed to existing · 1 new sense(s) proposed The two Māṇḍūkyabhāṣya passages (4 and 10) explicitly identify svapnasthāna with taijasa, the second quarter, and (in :10) correlate it with the ukāra of OM via utkarṣa and ubhayatva — squarely matching existing sense s1; routed there without modification. The three Āgamaśāstrabhāṣya passages instead use svapnasthāna as the dream-locale/abode of the dreaming subject: 2.8 speaks of svapnasthānavat draṣṭṛ and the sthānidharma (peculiar properties of the dream-place), 2.9 of mental constructs arising within the dream-place, and 4.63 of the dreamer wandering and perceiving beings 'in dream, in the dream-place.' This locative 'dream-as-place inhabited by the dreamer' sense is not represented in s1, so it is grouped under a new proposed sense s2. All five new loci are accounted for exactly once.
Caveats
The corpus here consists of a single mūla locus (Māṇḍūkya 10); no commentary loci from Gauḍapāda or Śaṅkara were supplied, so no witness positions can be attributed.
Only one stratum (the Māṇḍūkya mūla) is attested; no stratum-relative differentiation of senses is possible from the supplied evidence.
The phrase 'utkarṣād ubhayatvād vā' is given by the verse as the reason for the u/svapnasthāna correlation; whether utkarṣa means 'exaltation' or 'intermediacy/being drawn out' is not adjudicated within the supplied text.