pcb loop chip antenna impedance confusion

[electronx]

1001312 I have a 50 ohm 2485MHz chip antenna.
I have to adjust the s11 parameters for the antenna to work at the frequency I want, yes, everything seems fine in this case.
However, when I measure the z11 parameters from the antenna transeivcer feed point, I see a value like 36 ohms.
Shouldn't I see 50 ohms here?
I see 36 ohm impedance at 2.441 ghz, it provides s11 parameters but in this case maximum power transfer cannot be done according to maximum power theory.

in this case when I increase the impedance to 50 ohms, s11 parameters shift towards 2.7 ghz.

Can I keep the s11 parameters at 2.441 ghz center frequency with the correct values ​​and pull the feed impedance to 50 ohms?

[electronx]

My mistake, I looked in db.