My account is got hacked?

Now im facing issue regarding gmail account, i didn`t get to this kind of issue ever before.

Usually, i won't log in using any other device rather than my own devices.

also, i didn`t share any sensitive details such as username, password or mobile number with anyone..

but my ive got an email from gmail (original source) saying there was an unusual login activity. according to the details my usual IP address was given.

but there was a small change, it says logined using chrome version 61. but ive the version 71 (which was updated 2 months back itself).

so how does it possible, do Google make such mistakes?