Hello Alan,
Yes, both are correct, the size limit for modbus database is 1.2MB. to avoid allocating more memory required by the device itself for other processes.
Teltonika devices can store up to 20,000 modbus records, so it really depends on the size of the modbus records itself. Once the 20,000 has been reached, it will just overwrite to oldest data, keeping it at the mentioned limit.
Therefore, you can have 20,000 records existing on the db, but due to the smaller size and/or data type, the size of the database may not even reach the mentioned size limit (1.2 MB).
Best regards,
Rob