How to include only one symbol in your brute force?

[alibaba40]

When you are using ?a?a?a?a?a you are basically telling hashcat to use ?l?u?d?s on each character. I was wondering is there a way that ?s will only search for @ instead of all symbols?
That will reduce my cracking time.

[marc1n]

-1 ?a -2 @ ?1?1?1?1?2

https://hashcat.net/wiki/doku.php?id=mask_attack

[alibaba40]

-1 ?a -2 @ ?1?1?1?1?2

https://hashcat.net/wiki/doku.php?id=mask_attack

Thank you Sir