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

1. Adding

   #define ARDUINOJSON_USE_LONG_LONG 1
   

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

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

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

1. Adding

   #define ARDUINOJSON_USE_LONG_LONG 1
   

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

2. 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<T>(). This last page states that the method as<unsigned long long>() “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.