When C6 contains the value 64, and you a looking for 64; use:

C6=OFFSET(D1, COUNTIF(D1: D44,"<" & VALUE(C5)) ,0)

When C6 contains the value 64, and you a looking for 69.75; use:

C6=OFFSET(D1, COUNTIF(D1: D44,"<=" & VALUE(C5)) ,0)

This is making the assumption your LookUpList IS in ascending order as you
present in your example.

One observation: When C5 contains 3, it is less than the smallest value in your
LookUpList. I would add additional logic to advise your number  in C5 does not
'enter' the LookUpList. I'll assign this value as zero "0".
The logic expression looks like:
IsC5InTheLookUpList?=COUNTIF(D1:D44,"<=" & VALUE(C5))>0
This returns "True" when the CountIf( ) expression is greater than zero.
This returns "False" when the CountIf( ) expression is <= to zero.
A "True" result indicates there is a value C5 can be compared against in the
LookUpList. A "False" result indicates you are below the LookUpList smallest
value. Does that make sense? If so, make a change to the 'corrected' expression
from above:

C6=(OFFSET(D1, COUNTIF(D1: D44,"<" & VALUE(C5)) ,0)) * (IsC5InTheLookUpList?)

for a final expression:

C6=(OFFSET(D1, COUNTIF(D1: D44,"<" & VALUE(C5)) ,0)) * (COUNTIF(D1:D44,"<=" &
VALUE(C5))>0)