Does Create Membership v1 (API POST) return membership ID or junction ID?

https://developer.sky.blackbaud.com/api#api=membership&operation=CreateMembership

https://api.sky.blackbaud.com/membership/v1/constituents/{constituent_id}/membership

Returns this:

{    "id": "120"}

Is that the membership ID or junction ID?

In other words, from this pull:

constituent/v1/constituents/1357056/memberships

Does it correspond to id or members[0].id:

{
"count": 1,
"value": [
{
"id": "570907", ← This
…
"members": [
{
"id": "425069", ← Or this
"constituent_id": "1357056",
"primary": true
}
],
…
}
]
}