From “man find” & stackexchange

-exec command {} +

This  variant  of  the  -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the
end; the total number of invocations of the command will be much less than the number of matched files.  The command line is built in much  the  same  way  that
xargs builds its command lines.  Only one instance of `{}’ is allowed within the command.  The command is executed in the starting directory.