Each firewall needs its own license even if they are a HA pair. so 4 licenses..
there are default license that come with the device:
https://www.cisco.com/c/en/us/products/collateral/security/secure-firewall/guide-c07-737902.html
L-F9K-ASA(=) (for the Cisco Firepower 9300), L-FPR4100-ASA(=) (for the Cisco Firepower 4100 Series models), L-FPR3100-ASA(=) (for the Cisco Secure Firewall 3100 Series models), L-FPR2100-ASA(=) (for the Cisco Firepower 2100 Series models) or L-FPR1000-ASA(=) (for the Cisco Firepower 1000 Series models) and FPR42xx-BSE (for the Cisco Secure Firewall 4200 Series models): Licensing on the ASA is simplified for the Cisco Firepower appliances. More than 50 ASA feature licenses are condensed into a single license. This license also includes the following security contexts by default: 10 security contexts for Firepower 9300, 10 security contexts for Firepower 4100 Series, 10 security contexts for Secure Firewall 4200, 2 security contexts for Secure Firewall 3100 Series, 2 security contexts for Firepower 2100 Series and 2 security contexts for Firepower 1000 Series.
