Data analysed on the page below paints a picture of a large amount of non-marginal Tory seats with an above average leave vote. Most of these seats would not normally be Labour target seats.
There are, however, a number of Scottish marginal seats, mostly held by the SNP, which are marginal and have a very low leave vote.
There isn’t a single way to interpret this data.
One way is to say that if Labour want to gain a majority in the next general election (if as seems increasingly likely, this happens before the UK actually leaves the EU), then Labour needs to gain some of these Tory leave seats.
Another, and more intriguing way is to say that Labour could lose some remain seats they gained in the 2017 general election by chasing these Tory leave seats and ultimately get nowhere.
There are almost no leave seats which are marginals, whereas many marginals are remain seats. If Labour could take a lot of the SNP and Tory seats in Scotland, and then a few English and Welsh remain seats, even though an outright majority would be unlikely, they could be on the way to creating an effective coalition.