Just a reminder: when your partner opens the bidding and RHO overcalls 1NT, you should double (which is penalty) with any 10 HCP hand. Also double with a good 9 or even 8 HCP if you have a great lead.
You may choose not to do so when partner has opened third hand as s/he may be light.
If you bid over their NT overcall, you are showing a WEAK hand (not enough to double) but a long suit—at least 6 cards. Your bid is totally "Don't write; don't call. Let's hope I make this." Partner is not to take any action (even if s/he hates your suit).