3GPP 24.501 v20.0.0 — the document's own text
8.2.18.9 Lower bound 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 AMF may include this IE when the 5GMM cause is set to #78 "PLMN not allowed to operate at the present UE location", to provide a minimum time value for an entry added to the list of "PLMNs not allowed to operate at the present UE location".