From HEXONET Wiki
Transfer Pending Period
The Transfer Pending Period is a timeframe between a request from registrar (registrar A) to transfer a domain which the registrar of the domain (registrar B) may explicitly approve or reject . The timeframe is mostly a number of calendar days. The transfer will be finalized upon receipt of explicit approval or rejection from the current registrar (registrar B).
If the current registrar (registrar B) does not explicitly approve or reject the request initiated by registrar A, the registry will finalize (approve or deny) the request automatically after the end of the Transfer Pending Period.
This feature is also called AUTO-ACK or AUTO-NACK. Please have a look at Transfer Expire Action to see the effective behaviour of a registry.