Discrepancy between Account JSON schema and the Resource Content online

Looking at the Resource Content at http://www.hl7.org/fhir/account.html, it appears that the “subject” key is listed as an Array of References, however, in the JSON schema downloaded from http://hl7.org/fhir/2018May/validation.html, in “Account.schema.json” the subject key appears to be just a single Reference.
The site displays it as:
While the “Account.schema.json” file displays it as
“subject”: {
“description”: “Identifies the patient, device, practitioner, location or other object the account is associated with.”,
“$ref”: “Reference.schema.json#/definitions/Reference”
Im not sure which of these two definitions is correct. For example if the json were to be identical to the definition on the website, then it would look like:

"subject": {
"description": "the description",
"type": "array",
"items": {
"$ref": "Reference.schema.json#/definitions/Reference"

Is anyone able to provide clarification on this subject?

hl7.org/fhir and hl7.org/fhir/2018May are two different versions of the FHIR specification. The former was (until today) the official R3 version of the specification, which was published in 2017. 2018May was a ballot version working towards approval of R4. R4 is now complete and in the process of being published. Once that finishes (tonight or sometime tomorrow morning), R3 will be available at hl7.org/fhir/STU3.

Oh I see, thank you for that clarification!