Derive values from previous Quarters

I have a table called Hyp with below data

Quarter Target Date
Q1      50     Dec 31,2023
Q2      65     Mar 30,2024
Q3      90     June 30, 2024
Q4      120    Sep 30, 2024

Basically the targets are incremental counts and trying to derive like below:

Quarter Target
Q1      50
Q2      15
Q3      25
Q4      30

Q2 target will be Q2 Target - Q1 target

Wrote a DAX below but it is returning blank:

prevQtr = CALCULATE(SUM('Hyp'[taregt]), PREVIOUSQUARTER('Hyp'[Date]))

So first I created a calculated column for the quarter to get the number:

QuarterNumber = 
SWITCH(
    'Hyp'[Quarter],
    "Q1", 1,
    "Q2", 2,
    "Q3", 3,
    "Q4", 4,
    BLANK()
)

Then I created another calculated column for the incremental target :

Incremental Target = 
VAR CurrentQuarterTarget = 'Hyp'[Target]
VAR CurrentQuarterNumber = 'Hyp'[QuarterNumber]
VAR PreviousQuarterTarget = 
    CALCULATE(
        MAX('Hyp'[Target]),
        FILTER(
            'Hyp',
            'Hyp'[QuarterNumber] = CurrentQuarterNumber - 1
        )
    )
RETURN
IF(
    ISBLANK(PreviousQuarterTarget),
    CurrentQuarterTarget,
    CurrentQuarterTarget - PreviousQuarterTarget
)

So I try to get the target value and the quarter number of the current row. so I can calculate the target value of the previous quarter and check if there is no previous quarter and return the current target. Otherwise, I count the difference between the current target and the previous quarter's target.