In chapter 6.3. there is a query
FROM
EHR [ehr_id/value=$ehrUid] CONTAINS COMPOSITION [openEHR-EHR-COMPOSITION.encounter.v1]
CONTAINS OBSERVATION obs [openEHR-EHR-OBSERVATION.blood_pressure.v1]
WHERE
obs/data[at0001]/events[at0006]/data[at0003]/items[at0004]/value/value >= 140
The part with the "value/value" has to be "value/magnitude".
There could be some more occurences of this kind of typo in the AQL specification.
Similiar in Section 2.3