maybe the .size property comes from the ArcGIS Rest API Users, groups, and items Item Resources, but if that were the case, shouldn't we access the "resources" key first, get the desired index, then calling the .size property rather than accessing the .size property directly?:
{
"total": <total number of resources on the item>,
"start": <the first record index in the response>,
"num": <the number of resources in the response>,
"nextStart": <the next entry index>,
"resources": [
{
"resource": "<resource1>",
"created": <resource1 created datetime>,
"size": <resource1 size>
},
{
"resource": "<resource2>",
"created": <resource2 created datetime>,
"size": <resource2 size>
},
{
"resource": "<resource3>",
"created": <resource3 created datetime>,
"size": <resource3 size>
}
]
}