A method of controlling an indication of user data in a buffer of a User Equipment (UE) is provided. The user data is for Small Data Transmission (SDT) when the UE is in inactive mode. Based on a threshold value related to an amount of the user data for SDT, the UE determines whether to include an indication into a first uplink grant allocation transmission. The indication would indicate that user data is in the buffer. When an indication of user data in a buffer is not included in the first uplink grant, this indicates that the amount of data left in the buffer is less than the threshold value minus the first allocated grant transmission size, and when an indication of user data in a buffer is included, the indication indicates how many further transmissions are needed for transmitting the rest of the pending data.