EDIT: Here is the page with Merrick from the Origin comic. This scene is based on the TV episode Becomming, Part 1, and not the movie, meaning it ties in with the series better.
From wikipedia:
Continuity
Canonical issues
Main article: Buffyverse canon
Buffy comics such as this one are not usually considered by fans as canonical. However, Christopher Golden used Joss Whedon's original script for the Buffy movie, and tied this comic series closely to continuity established by the television show. For example, the burning down of the gym takes place, which is mentioned several times on the show. For this reason, some fans argue that this comic deserves a place in canon.
* The story is framed not as actual events but how Buffy remembers them (she is telling Willow and Xander the story of how she found out she was a Slayer). This fact may help explain inconsistencies (for example, the bat-like appearance of the vampires). It is also possible she exaggerated the neglective behaviour of her parents.
* In the story there is the implication that the vampires required an inviation to enter the gym. Canon is divided over whether vampires need an invite to enter a public building, for example, in the episode School Hard, Spike invades the school with no invite needed, whereas in the same season in Passion, Angel tells Jenny he was invited by the inscription 'Enter all who seek Knowledge', so whether some vampires are simply mistaken over the technicalities of their vampiredom is unclear.
Timing
* Supposed to be set in Spring of 1996, several months before Buffy moves to Sunnydale in "Welcome to the Hellmouth". This comic stands in place of the Buffy movie, which is not considered to be canonical.
The writers, Scott Lobdell, Fabian Nicieza, and Paul Lee made a strong effort to offer a non-contradictory continuity filling the gap between the events of this comic, and "Welcome to the Hellmouth"