what is the meaning of "Max Insert Size" in Backup Database

Dear HeidiSQL Developer,

I need to know what is the meaning of "Max Insert Size" in then Backup Database? if i leave it as default (1.024 Kb) and meanwhile the size of my DB is 56 MB. Is it OK for me to get backup my DB with this choice?

Yes, that's just the maxium size of chunks with extended INSERT statements, into which HeidiSQL divides the data. The size is important because if you send too large statements with lots of value sets:

INSERT INTO.. VALUES (...), (...), ...

... that may break the connection when you import it.

See also https://dev.mysql.com/doc/refman/5.7/en/packet-too-large.html