A Issue for OP_PushBytes

[cyl19970726]

let scripts3 = script!{
            0x90
            OP_DROP
            OP_1
        };

My expect output is "P_PUSHBYTES_1 90 OP_DROP OP_PUSHNUM_1", but the actual output is "OP_PUSHBYTES_2 9000 OP_DROP OP_PUSHNUM_1"
What causes this problem？