Tested with https://github.com/zimeon/oaipmh-validator
and curl -s "baseURL?verb=ListRecords&metadataPrefix=oai_dc" | xmllint --format - | grep resumptionToken
### Checking for correct use of resumptionToken (if used)
REQUEST: baseURL?verb=ListRecords&metadataPrefix=oai_dc GET
FAIL: A cursor value was supplied with the resumptionToken but it did not have the correct value zero for the first response. The value was '50'.
This value is OAI-PMH:MaxCount syspref.
_cursor_ indicate the number of previous replies have already delivered: "cursor -- a count of the number of elements of the complete list thus far returned (i.e. cursor starts at 0)."