What does the colon operator indicate when used with declaration [duplicate]

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• “:” (colon) in C struct - what does it mean? [duplicate] 3 answers

I am working on a project which uses C++98, I found a code snippet like

#include <stdint.h>
class Toy {
    int64_t lID;
    int64_t eID : 48;
    short pID : 16;
};

I understand what int64_t does but am not able to understand the significance ": 48" and ": 16". Can someone please help me?