Why does Play Store update twice in a row the same app to the same version?
Update: It is probably a "hot fix" of application developers, which they've spotted few moments after the update release. As solution it is easier to release an immediate second update with the same version number (ver. numbering is solely on app developer). So it ends up twice (or even several times) after the first update. Also, IMHO, the same version number ensures that users, who did not updated with the first "buggy" wave, will receive the last "hot fixed" update of that number. This was confirmed in some case here.

Original post:

Maybe this issue is connected with multiple google accounts? It could be intersting to check next time this happens if both update proposals are for the same account.

Second thought: did the update go well in the first attempt?