Insights into the inner structures of the fully charmed tetraquark state <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>X</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>6900</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:math>

The recently discovered fully charmed tetraquark candidate $X(6900)$ is analyzed within the frameworks of effective-range expansion, compositeness relation and width saturation, a coupled multichannel dynamical study. By taking into account constraints from heavy-quark spin symmetry, coupled-channel amplitude including $J/\ensuremath{\psi}J/\ensuremath{\psi}$, ${\ensuremath{\chi}}_{c0}{\ensuremath{\chi}}_{c0}$, ${\ensuremath{\chi}}_{c1}{\ensuremath{\chi}}_{c1}$ constructed to fit experimental di-$J/\ensuremath{\psi}$ event distributions around energy region near 6.9 GeV. Another two-coupled-channel with $J/\ensuremath{\psi}J/\ensuremath{\psi}$ $\ensuremath{\psi}(3770)J/\ensuremath{\psi}$ also considered describe same datasets. three different theoretical approaches lead similar conclusions that two-meson components do not play dominant roles in $X(6900)$. Our determinations resonance poles complex plane refined study are found be consistent analyses. amplitudes have another pole corresponding narrow $X(6825)$ we predict sitting below ${\ensuremath{\chi}}_{c0}{\ensuremath{\chi}}_{c0}$ threshold molecular origin. We give predictions line shapes channels, which could provide useful guide for future measurements.