I thought that this would have been a common problem but I haven't found anything similar to my issue.

For Row 5 starting with Column C and ending with column F, I entered in this data: 8.20 a 11.00 a. Basically I want to calculate duration of time by entering data such that the decimal is equivalent to ":". I.e. 8.20 = 8:20. Maybe there is a better way to solve this issue but I don't know how to subtract time notation if possible, i.e 11:00a - 8:20a = 2.67 hours. What my formula is doing is counting the 2 as a one-digit number rather than in the 10s place (2 instead of 20). Not sure how to amend that to where 8.20 = 500, 8.02 = 482.

=IFERROR((((VALUE(LEFT(E5,2))+IF(F5="p",IF(AND(E5>=12,E5<13),0,12),IF(F5="a",IF(AND(E5>=12,E5<13),12,0),"")))*60+VALUE(IF(MID(E5,IF(AND(E5<13,E5>=10),4,3),2)="",0,MID(E5,IF(AND(E5<13,E5>=10),4,3),2))))-((VALUE(LEFT(C5,2))+IF(D5="p",IF(AND(C5>=12,C5<13),0,12),IF(D5="a",IF(AND(C5>=12,C5<13),12,0),0)))*60+VALUE(IF(MID(C5,IF(AND(C5<13,C5>=10),4,3),2)="",0,MID(C5,IF(AND(C5<13,C5>=10),4,3),2)))))/60,"")
Sorry if my code is a bit inefficient. Data is constantly being added to columns C through columns F.