It can sometimes be confusing to know what it means when you double and then bid again.
Here are the main 3 instances:
1) You make a takeout double and bid again
2) You make a negative double and bid again
3) You double their 1NT overcall and bid again
1) You make a takeout double and bid again
This shows the "big double" (approximately worth 17/18+). Such an auction shows a "big" hand, but not too big, because partner can pass.
Typical
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