New tape is used to continue backup when there is free space on previous tape.
Backup archive uses more tapes than required by its size: e.g. 14GB backup archive uses 17 tapes of 1 GB size.
This behavior is based on tape device logic: when Acronis Cyber Backup receives internal message from tape appliance that tape media is almost full, it stops writing to it in order to avoid potential issues. The amount of free space left on tape media depends on tape device vendor and model, but typically it should be insignificant (about 3-5% of total capacity).
Early Warning End Of Tape (EWEOT) is a band or signal near the end of tape, added by the manufacturer, to let the tape backup software know that end of tape is almost reached.
Latest builds of Acronis Cyber Backup 12.5 and Acronis Cyber Backup Cloud report the remaining free space based on the actual space where data can be written. Please update to the latest build.
Updating the drivers for the tape device may improve tape device behavior concerning early warning about end of tape.