How could I get a current lower than 1e-12A on a node?

Dear All,
When I do simulation about a RPA,I found that it seems that if collecting current of an electric node lower than 1e-12A,the result is 0A.
Is there some limitation in the software during calculating the collected current? How could I improve the precision of the collecting current? Is there any parameters in the software?

Any suggestion is appreciate.

Best Regards,

Dear Guan,

could you please precise what you meant by “lower than 1e-12A,the result is 0A”? Is it on the display of an instrument result?