Large number into variable
I didn't try myself, but just by looking at the docs I suggest you try:


Adding


#define ARDUINOJSON_USE_LONG_LONG 1


at the top of the sketch, before including ArduinoJson.h.


Declare CurrentUpdatedMS and CurrentUpdatedMS as either
unsigned long long or uint64_t.


Edit: To answer the question in the comment:


  When you said you looked at the docs where did you check?


I had to follow a (not so simple) path: Deserialization tutorial →
JsonDocument::operator[] → JsonVariant →
JsonVariant::as&lt;T&gt;(). This last page states that the method
as&lt;unsigned long long&gt;() “may require ARDUINOJSON_USE_LONG_LONG”.
Unfortunately, the macro is not linked, so I have to search for it and
found ARDUINOJSON_USE_LONG_LONG.