Adtran Holdings Inc. ADTN shares dropped 9.96% to $9.40 in after-hours trading on Monday after announcing a$150 million convertible senior notes offering.According to Benzinga Pro data, the stock closed regular trading at $10.44, up 3.26%.Check out the current price of ADTN stock here.Notes Structure And TermsThe Huntsville-based networking company plans to offer convertible notes due in 2030 through a private placement to qualified institutional buyers. Initial buyers will have the option to purchase an a ...