A question about the Humble Choice annual plan

You bought 12 picks.
So, if you pause for a month you save this pick and can use it for a other month.

So yes, the plan be extented by 1 month in this case.

Buying the plan gives you 12 credits for bundles, a credit is only used if you claim the games for that month (or they are auto-claimed at the end of the month). Pausing for the month will not use a credit.

Humble has this covered on their support page, under FAQ:
https://support.humblebundle.com/hc/en-us/articles/1260801750469-Humble-Choice-Automatic-Billing-and-Content-Release-Dates

Simplified, you buy 12 credits and you can still choose what months to use them. So you can be on an annual plan that will end in more than 12 months from time of subscribing.

Note: Even if you skip it, sometimes it may be canceled or automatically paid when the payment date approaches. In that case, please check and request to stop or cancel the payment again.

Note that claiming the code will purchase the current month, so make sure you redeem in a month that you want.