colon followed immediately with a hyphen

[Basharuae]

I’ve seen correspondences/ writings carry the punctuation mark colon followed immediately with a hyphen when making a list afterward, as per the example below. I tried to look this up but could not find any rule.

Any ideas please?

The followings items were purchased yesterday :-

[Josef Essberger]

As far as I know this is just a variation of the colon, usually according to personal preference.

By the way, there is normally no space before it, so your example should be:

The followings items were purchased yesterday:-

[Basharuae]

Hi Josef

I traced down and found nothing GRAMMATICALLY to support this use, on the contrary people are advised not to use this thing.

thanks anyway