For oversubscribed retail categories, regulation requires that the maximum number of applicants receive at least one lot, so allotment is decided by lottery rather than proportionally.
If you do not receive an allotment, the amount blocked through the UPI mandate is released back to your bank account.
An easy example
If the retail category is subscribed 3 times, only about one in three retail applicants may receive a single lot, decided by a computerised draw.
Important note
The registrar handles allotment and publishes a status page where you can check with your PAN or application number.
Common mistake
Expecting a refund the same day. Blocked funds are usually released one to two working days after allotment is finalised.