Units calculation error for derived units

[iomaganaris]

When calculating values of derived units from other units when needed to do a calculation like multiplication or division there is an error in the computed values by mod2c and NEURON.
For example for:

UNITS {
	R = 8.313424 (joule/degC)
	J = (R-mole) (1)
	test = (mole) (1)
}

We have with NEURON:

 static double R = 8.313424;
#define J _nrnunit_J[_nrnunit_use_legacy_]
static double _nrnunit_J[2] = {0x1.0912acba81b67p+82, 5.00711e+24}; /* 5.00708642302769403e+24 */
#define test _nrnunit_test[_nrnunit_use_legacy_]
static double _nrnunit_test[2] = {0x1.fe185ca57c517p+78, 6.02217e+23}; /* 6.02214075999999987e+23 */
static int _reset;
static char *modelname = "CaGk";

With mod2c:

double R = 8.313424;
#pragma acc declare copyin(R)
double J = /* 0x1.0912acba81b67p+82; */ 5.00708642302769403e+24;
 #pragma acc declare copyin(J)
double test = /* 0x1.fe185ca57c517p+78; */ 6.02214075999999987e+23;
 #pragma acc declare copyin(test)
static const char *modelname = "CaGk";

With NMODL:

/** constants used in nmodl from UNITS */
    static const double R = 8.313424;
    static const double J = 5.00646095255622339e+24;
    static const double test = 6.02214075999999987e+23;

From the above we see that mole = 6.02214075999999987e+23, R = 8.313424 and if we calculate by hand J = R*mole we have:

>>> 6.02214075999999987e+23 * 8.313424
5.006460952556223e+24

This value is the same with NMODL, however the values in mod2c and NEURON are different