In "Vanka" by Anton Chekhov, the narrative is interlaced with epistolary passages. An epistolary passage is one in which a character either writes a letter (epistle) or reads a letter. In this case, the epistolary passages comprise a letter being written by Vanka. In an epistle, the point of view is generally first person (unless perhaps the content is of the they said/you said variety). However, when an epistle is embedded in a larger narrative, the epistle takes on the role of a dialogic insertion (dialogic: pertaining to dialogue) and is analysed as any other dialogic passage would be.
Consequently, since dialogue in a narrative doesn't not change the story's point of view, neither does a dialogic epistolary insertion in a narrative change the story's point of view. Therefore, the first person point of view within the the epistle doesn't affect the analysis of the point of view of the story. If you look at the text of "Vanka," you can see that this is true because the epistolary passages are all set off by quotation marks--they are considered and analyzed as dialogue.
The conclusion is that, while the point of view within the dialogic epistolary insertions is first person, the story of "Vanka" is written solely in the third person limited point of view: The narrator sees and conveys the story while looking over the shoulder--if you will--of Vanka while he writes his letter. So even though Vanka's voice intrudes into the narrative, it is spoken, as it were, by the third person limited narratorial voice, a voice that is, so to speak, reading aloud to the story reader from Vanka's private letter. Thus it is incorrect to state that the short story "Vanka" has two points of view: "Vanka" has one point of view (third person limited) and the embedded epistolary dialogue (letter) presents an embedded first person point of view.