3GPP 24.501 v20.0.0 — the document's own text
8.3.3.2 Back-off timer value
Taught in 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).
The network may include this IE if the 5GSM cause is not #28 "unknown PDU session type", #39 "reactivation requested", #46 "out of LADN service area", #50 "PDU session type IPv4 only allowed", #51 "PDU session type IPv6 only allowed", #54 "PDU session does not exist", #57 "PDU session type IPv4v6 only allowed", #58 "PDU session type Unstructured only allowed", #61 "PDU session type Ethernet only allowed",#68 "not supported SSC mode", or #86 "UAS services not allowed" to request a minimum time interval before procedure retry is allowed.