Worrying about the OG at the 3rd decimal point isn't practical, most of our volume measurements have too much error. Also, the fermentability of extract varies quite a bit so it is going to vary.
If you are plus or minus .005 no worries. If it's off more than that just adjust with water or extract. It very hard to get a good OG reading if doing partial boils due to the incomplete mixing of high gravity wort and plain water. If you are doing full boils, your OG readings should be pretty accurate, just remember to correct for temperature.
Something is always fermenting
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