how to use metric scale ruler

{"cid":"91204360","title":"5um 3 Axis Digital Readout DRO SDS6-3V 5micron Linear Encoder KA300 Glass Scale Ruler","imgUrl":"https:\/\/img.ismap.com\/nimg\/27\/cb\/794bfd2e2f7c0b2d20597582aef2-200x200-1.jpg","attrs":{"Price":"Negotiable","Brand Name":"SINO","Model Number":"SDS6-3V, KA300, Ka500","Minimum Order Quantity":"1 PC","Delivery Time":"5-8 days","Certification":"CE,RoHS","Place of Origin":"Guangzhou, CHINA","Payment Terms":"T\/T, L\/C, Western Union, MoneyGram","Supply Ability":"1000 pcs per month","Packaging Details":"Carton","Name":"SDS6-3V Optical Ruler KA300 Glass linear scale","Number of Axis":"3 axis Dro + Ka500 ka300","Color":"Grey","Signal":"Digital readout: TTL \/ RS422","Voltage":"Digital readout: AC100-240V \/ 50-60Hz","Suitable for":"Milling machine, boring machine","Resolution":"1um,5um,0.5um"}}

{"cid":"91218857","title":"Waterproof Adhesive Workbench Ruler Tape for Boat Kayak and Table Dual Scale Fish Tape","imgUrl":"https:\/\/img.ismap.com\/nimg\/39\/68\/a61e38e6094b275efe0b76e19355-200x200-1.jpg","attrs":{"Brand Name":"Wintape or customized","Model Number":"BT-102","Minimum Order Quantity":"1000","Delivery Time":"20-25days","Place of Origin":"China","Payment Terms":"T\/T, Western Union","Supply Ability":"6000pcs\/day","Packaging Details":"Each piece rolled, 1000pcs\/carton NW\/GW:5\/6kgs Carton Size: 37*29*27cm","Material":"PVC plastic sticker","Size":"60cm","Scale":"cm on one side","Design":"Customized","Colorsilver":"silver color with black printing"}}