By default, Microsoft has restricted the download size of the list template as 10MB (10485760 bytes). If you are trying to save site/list template which are having more than 10MB size, you will get “The list is too large to save as a template. The size of a template cannot exceed 10485760 bytes.” error.

To resolve this issue, you have to run the below command in the command prompt:
stsadm -o setproperty -propertyname max-template-document-size -propertyvalue 524288000
You can increase the maximum size of a list / site template by running the following command (note that 500mb is the largest you can go):

stsadm -o setproperty -propertyname max-template-document-size -propertyvalue 50000000