For One-to-one Chat Message:

1 green tick - Message is successfully received by SeaTalk server 

2 green ticks - Message is successfully delivered to the receiver

2 blue ticks - Message is read by the receiver

For Group Chat Message:

1 green tick - Message is successfully received by SeaTalk server

2 green tick - Message is successfully received by all group members

2 blue ticks - Message is read by all group members