Integer overflow detected in keyspace of mask

[crinny]

I have a hashed string that goes something like this: 392428176.27.938888368973832043. The length is always constant, and the first value (392428176 in this case) is already known. I have made the following mask for hashcat:

Code:

392428176.?d?d.?d?d?d?d?d?d?d?d?d?d?d?d?d?d?d?d?d?d

But upon running the hashcat (hashcat -m 0 -a 3 hash.txt mask.hcmask), I am getting this error: Integer overflow detected in keyspace of mask.
As far as I am aware, there are 20^10 possibilities of my mask. What is going wrong?