求翻译：如果招标文件列出了建议的开采地，并说明仅供承包商参考，承包商应在现场考察中对是否能开采出符合合同要求的材料做出客观的评判，必要时可开展少量试验，以得到可靠的结果，使得报价更加准确。是什么意思？

If the file lists the proposed mining of land by tender, and instructions are only for reference of operators, contractors should be in the field study on whether out of material to make an objective evaluation of the compliance with contract requirements, if necessary, carry out a small amount of testing, and to obtain reliable results, makes quotes more accurate.